21 Nov, 2015
1 commit
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When building kernel with gcc 5.2, the below warning is raised:
mm/page-writeback.c: In function 'balance_dirty_pages.isra.10':
mm/page-writeback.c:1545:17: warning: 'm_dirty' may be used uninitialized in this function [-Wmaybe-uninitialized]
unsigned long m_dirty, m_thresh, m_bg_thresh;The m_dirty{thresh, bg_thresh} are initialized in the block of "if
(mdtc)", so if mdts is null, they won't be initialized before being used.
Initialize m_dirty to zero, also initialize m_thresh and m_bg_thresh to
keep consistency.They are used later by if condition: !mdtc || m_dirty
Cc: Tejun Heo
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
13 Oct, 2015
4 commits
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For memcg domains, the amount of available memory was calculated as
min(the amount currently in use + headroom according to memcg,
total clean memory)This isn't quite correct as what should be capped by the amount of
clean memory is the headroom, not the sum of memory in use and
headroom. For example, if a memcg domain has a significant amount of
dirty memory, the above can lead to a value which is lower than the
current amount in use which doesn't make much sense. In most
circumstances, the above leads to a number which is somewhat but not
drastically lower.As the amount of memory which can be readily allocated to the memcg
domain is capped by the amount of system-wide clean memory which is
not already assigned to the memcg itself, the number we want isthe amount currently in use +
min(headroom according to memcg, clean memory elsewhere in the system)This patch updates mem_cgroup_wb_stats() to return the number of
filepages and headroom instead of the calculated available pages.
mdtc_cap_avail() is renamed to mdtc_calc_avail() and performs the
above calculation from file, headroom, dirty and globally clean pages.v2: Dummy mem_cgroup_wb_stats() implementation wasn't updated leading
to build failure when !CGROUP_WRITEBACK. Fixed.Signed-off-by: Tejun Heo
Fixes: c2aa723a6093 ("writeback: implement memcg writeback domain based throttling")
Signed-off-by: Jens Axboe -
MDTC_INIT() is used to initialize dirty_throttle_control for memcg
domains. It used DTC_INIT_COMMON() to initialized mdtc->wb and
->wb_completions which is incorrect as DTC_INIT_COMMON() sets the
latter to wb->completions instead of wb->memcg_completions. This can
lead to wildly incorrect results when calculating the proportion of
dirty memory the memcg domain should get.Remove DTC_INIT_COMMON() and update MDTC_INIT() to initialize
mdtc->wb_completions to wb->memcg_completions.Signed-off-by: Tejun Heo
Fixes: c2aa723a6093 ("writeback: implement memcg writeback domain based throttling")
Signed-off-by: Jens Axboe -
bdi_for_each_wb() is used in several places to wake up or issue
writeback work items to all wb's (bdi_writeback's) on a given bdi.
The iteration is performed by walking bdi->cgwb_tree; however, the
tree only indexes wb's which are currently active.For example, when a memcg gets associated with a different blkcg, the
old wb is removed from the tree so that the new one can be indexed.
The old wb starts dying from then on but will linger till all its
inodes are drained. As these dying wb's may still host dirty inodes,
writeback operations which affect all wb's must include them.
bdi_for_each_wb() skipping dying wb's led to sync(2) missing and
failing to sync the inodes belonging to those wb's.This patch adds a RCU protected @bdi->wb_list which lists all wb's
beloinging to that bdi. wb's are added on creation and removed on
release rather than on the start of destruction. bdi_for_each_wb()
usages are replaced with list_for_each[_continue]_rcu() iterations
over @bdi->wb_list and bdi_for_each_wb() and its helpers are removed.v2: Updated as per Jan. last_wb ref leak in bdi_split_work_to_wbs()
fixed and unnecessary list head severing in cgwb_bdi_destroy()
removed.Signed-off-by: Tejun Heo
Reported-and-tested-by: Artem Bityutskiy
Fixes: ebe41ab0c79d ("writeback: implement bdi_for_each_wb()")
Link: http://lkml.kernel.org/g/1443012552.19983.209.camel@gmail.com
Cc: Jan Kara
Signed-off-by: Jens Axboe -
laptop_mode_timer_fn() was using bdi_for_each_wb() without the
required RCU locking leading to the following warning.WARNING: CPU: 0 PID: 0 at include/linux/backing-dev.h:415 laptop_mode_timer_fn+0x106/0x170()
...
Call Trace:
[] dump_stack+0x4e/0x82
[] warn_slowpath_common+0x82/0xc0
[] warn_slowpath_null+0x1a/0x20
[] laptop_mode_timer_fn+0x106/0x170
[] call_timer_fn+0xb3/0x2f0
[] run_timer_softirq+0x205/0x370
[] __do_softirq+0xd4/0x460
[] irq_exit+0x89/0xa0
[] smp_apic_timer_interrupt+0x42/0x50
[] apic_timer_interrupt+0x84/0x90
...Fix it by adding rcu_read_lock() around the iteration.
Signed-off-by: Tejun Heo
Fixes: a06fd6b10228 ("writeback: make laptop_mode_timer_fn() handle multiple bdi_writeback's")
Reviewed-by: Jan Kara
Signed-off-by: Jens Axboe
11 Sep, 2015
1 commit
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Pull blk-cg updates from Jens Axboe:
"A bit later in the cycle, but this has been in the block tree for a a
while. This is basically four patchsets from Tejun, that improve our
buffered cgroup writeback. It was dependent on the other cgroup
changes, but they went in earlier in this cycle.Series 1 is set of 5 patches that has cgroup writeback updates:
- bdi_writeback iteration fix which could lead to some wb's being
skipped or repeated during e.g. sync under memory pressure.- Simplification of wb work wait mechanism.
- Writeback tracepoints updated to report cgroup.
Series 2 is is a set of updates for the CFQ cgroup writeback handling:
cfq has always charged all async IOs to the root cgroup. It didn't
have much choice as writeback didn't know about cgroups and there
was no way to tell who to blame for a given writeback IO.
writeback finally grew support for cgroups and now tags each
writeback IO with the appropriate cgroup to charge it against.This patchset updates cfq so that it follows the blkcg each bio is
tagged with. Async cfq_queues are now shared across cfq_group,
which is per-cgroup, instead of per-request_queue cfq_data. This
makes all IOs follow the weight based IO resource distribution
implemented by cfq.- Switched from GFP_ATOMIC to GFP_NOWAIT as suggested by Jeff.
- Other misc review points addressed, acks added and rebased.
Series 3 is the blkcg policy cleanup patches:
This patchset contains assorted cleanups for blkcg_policy methods
and blk[c]g_policy_data handling.- alloc/free added for blkg_policy_data. exit dropped.
- alloc/free added for blkcg_policy_data.
- blk-throttle's async percpu allocation is replaced with direct
allocation.- all methods now take blk[c]g_policy_data instead of blkcg_gq or
blkcg.And finally, series 4 is a set of patches cleaning up the blkcg stats
handling:blkcg's stats have always been somwhat of a mess. This patchset
tries to improve the situation a bit.- The following patches added to consolidate blkcg entry point and
blkg creation. This is in itself is an improvement and helps
colllecting common stats on bio issue.- per-blkg stats now accounted on bio issue rather than request
completion so that bio based and request based drivers can behave
the same way. The issue was spotted by Vivek.- cfq-iosched implements custom recursive stats and blk-throttle
implements custom per-cpu stats. This patchset make blkcg core
support both by default.- cfq-iosched and blk-throttle keep track of the same stats
multiple times. Unify them"* 'for-4.3/blkcg' of git://git.kernel.dk/linux-block: (45 commits)
blkcg: use CGROUP_WEIGHT_* scale for io.weight on the unified hierarchy
blkcg: s/CFQ_WEIGHT_*/CFQ_WEIGHT_LEGACY_*/
blkcg: implement interface for the unified hierarchy
blkcg: misc preparations for unified hierarchy interface
blkcg: separate out tg_conf_updated() from tg_set_conf()
blkcg: move body parsing from blkg_conf_prep() to its callers
blkcg: mark existing cftypes as legacy
blkcg: rename subsystem name from blkio to io
blkcg: refine error codes returned during blkcg configuration
blkcg: remove unnecessary NULL checks from __cfqg_set_weight_device()
blkcg: reduce stack usage of blkg_rwstat_recursive_sum()
blkcg: remove cfqg_stats->sectors
blkcg: move io_service_bytes and io_serviced stats into blkcg_gq
blkcg: make blkg_[rw]stat_recursive_sum() to be able to index into blkcg_gq
blkcg: make blkcg_[rw]stat per-cpu
blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead_stats with it
blkcg: consolidate blkg creation in blkcg_bio_issue_check()
blk-throttle: improve queue bypass handling
blkcg: move root blkg lookup optimization from throtl_lookup_tg() to __blkg_lookup()
blkcg: inline [__]blkg_lookup()
...
19 Aug, 2015
1 commit
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The following tracepoints are updated to report the cgroup used during
cgroup writeback.* writeback_write_inode[_start]
* writeback_queue
* writeback_exec
* writeback_start
* writeback_written
* writeback_wait
* writeback_nowork
* writeback_wake_background
* wbc_writepage
* writeback_queue_io
* bdi_dirty_ratelimit
* balance_dirty_pages
* writeback_sb_inodes_requeue
* writeback_single_inode[_start]Note that writeback_bdi_register is separated out from writeback_class
as reporting cgroup doesn't make sense to it. Tracepoints which take
bdi are updated to take bdi_writeback instead.Signed-off-by: Tejun Heo
Suggested-by: Jan Kara
Reviewed-by: Jan Kara
Signed-off-by: Jens Axboe
07 Aug, 2015
1 commit
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The initial value of global_wb_domain.dirty_limit set by
writeback_set_ratelimit() is zeroed out by the memset in
wb_domain_init().Signed-off-by: Rabin Vincent
Acked-by: Tejun Heo
Cc: Jens Axboe
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Jun, 2015
1 commit
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Pull cgroup writeback support from Jens Axboe:
"This is the big pull request for adding cgroup writeback support.This code has been in development for a long time, and it has been
simmering in for-next for a good chunk of this cycle too. This is one
of those problems that has been talked about for at least half a
decade, finally there's a solution and code to go with it.Also see last weeks writeup on LWN:
http://lwn.net/Articles/648292/"
* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
writeback, blkio: add documentation for cgroup writeback support
vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
writeback: do foreign inode detection iff cgroup writeback is enabled
v9fs: fix error handling in v9fs_session_init()
bdi: fix wrong error return value in cgwb_create()
buffer: remove unusued 'ret' variable
writeback: disassociate inodes from dying bdi_writebacks
writeback: implement foreign cgroup inode bdi_writeback switching
writeback: add lockdep annotation to inode_to_wb()
writeback: use unlocked_inode_to_wb transaction in inode_congested()
writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
writeback: implement [locked_]inode_to_wb_and_lock_list()
writeback: implement foreign cgroup inode detection
writeback: make writeback_control track the inode being written back
writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
writeback: implement memcg writeback domain based throttling
writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
writeback: implement memcg wb_domain
writeback: update wb_over_bg_thresh() to use wb_domain aware operations
...
02 Jun, 2015
31 commits
-
The mechanism for detecting whether an inode should switch its wb
(bdi_writeback) association is now in place. This patch build the
framework for the actual switching.This patch adds a new inode flag I_WB_SWITCHING, which has two
functions. First, the easy one, it ensures that there's only one
switching in progress for a give inode. Second, it's used as a
mechanism to synchronize wb stat updates.The two stats, WB_RECLAIMABLE and WB_WRITEBACK, aren't event counters
but track the current number of dirty pages and pages under writeback
respectively. As such, when an inode is moved from one wb to another,
the inode's portion of those stats have to be transferred together;
unfortunately, this is a bit tricky as those stat updates are percpu
operations which are performed without holding any lock in some
places.This patch solves the problem in a similar way as memcg. Each such
lockless stat updates are wrapped in transaction surrounded by
unlocked_inode_to_wb_begin/end(). During normal operation, they map
to rcu_read_lock/unlock(); however, if I_WB_SWITCHING is asserted,
mapping->tree_lock is grabbed across the transaction.In turn, the switching path sets I_WB_SWITCHING and waits for a RCU
grace period to pass before actually starting to switch, which
guarantees that all stat update paths are synchronizing against
mapping->tree_lock.This patch still doesn't implement the actual switching.
v3: Updated on top of the recent cancel_dirty_page() updates.
unlocked_inode_to_wb_begin() now nests inside
mem_cgroup_begin_page_stat() to match the locking order.v2: The i_wb access transaction will be used for !stat accesses too.
Function names and comments updated accordingly.s/inode_wb_stat_unlocked_{begin|end}/unlocked_inode_to_wb_{begin|end}/
s/switch_wb/switch_wbs/Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
While cgroup writeback support now connects memcg and blkcg so that
writeback IOs are properly attributed and controlled, the IO back
pressure propagation mechanism implemented in balance_dirty_pages()
and its subroutines wasn't aware of cgroup writeback.Processes belonging to a memcg may have access to only subset of total
memory available in the system and not factoring this into dirty
throttling rendered it completely ineffective for processes under
memcg limits and memcg ended up building a separate ad-hoc degenerate
mechanism directly into vmscan code to limit page dirtying.The previous patches updated balance_dirty_pages() and its subroutines
so that they can deal with multiple wb_domain's (writeback domains)
and defined per-memcg wb_domain. Processes belonging to a non-root
memcg are bound to two wb_domains, global wb_domain and memcg
wb_domain, and should be throttled according to IO pressures from both
domains. This patch updates dirty throttling code so that it repeats
similar calculations for the two domains - the differences between the
two are few and minor - and applies the lower of the two sets of
resulting constraints.wb_over_bg_thresh(), which controls when background writeback
terminates, is also updated to consider both global and memcg
wb_domains. It returns true if dirty is over bg_thresh for either
domain.This makes the dirty throttling mechanism operational for memcg
domains including writeback-bandwidth-proportional dirty page
distribution inside them but the ad-hoc memcg throttling mechanism in
vmscan is still in place. The next patch will rip it out.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Dirtyable memory is distributed to a wb (bdi_writeback) according to
the relative bandwidth the wb is writing out in the whole system.
This distribution is global - each wb is measured against all other
wb's and gets the proportinately sized portion of the memory in the
whole system.For cgroup writeback, the amount of dirtyable memory is scoped by
memcg and thus each wb would need to be measured and controlled in its
memcg. IOW, a wb will belong to two writeback domains - the global
and memcg domains.The previous patches laid the groundwork to support the two wb_domains
and this patch implements memcg wb_domain. memcg->cgwb_domain is
initialized on css online and destroyed on css release,
wb->memcg_completions is added, and __wb_writeout_inc() is updated to
increment completions against both global and memcg wb_domains.The following patches will update balance_dirty_pages() and its
subroutines to actually consider memcg wb_domain for throttling.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
wb_over_bg_thresh() currently uses global_dirty_limits() and
wb_dirty_limit() both of which are wrappers around operations which
take dirty_throttle_control. For cgroup writeback support, the
function will be updated to also consider memcg wb_domains which
requires the context information carried in dirty_throttle_control.This patch updates wb_over_bg_thresh() so that it uses the underlying
wb_domain aware operations directly and builds the global
dirty_throttle_control in the process.This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
and rename it to wb_over_bg_thresh(). The function is closely tied to
the dirty throttling mechanism implemented in page-writeback.c. This
relocation will allow future updates necessary for cgroup writeback
support.While at it, add function comment.
This is pure reorganization and doesn't introduce any behavioral
changes.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
global_dirty_limits() calculates thresh and bg_thresh (confusingly
called *pdirty and *pbackground in the function) assuming
global_wb_domain; however, cgroup writeback support requires
considering per-memcg wb_domain too.This patch separates out domain_dirty_limits() which takes
dirty_throttle_control out of global_dirty_limits(). As thresh and
bg_thresh calculation needs the amount of dirtyable memory in the
domain, dirty_throttle_control->avail is added. The new function
calculates the two thresholds and store them directly in the
dirty_throttle_control.Also, as memcg domains can't follow vm_dirty_bytes and
dirty_background_bytes settings directly. If those are set and
domain_dirty_limits() is invoked for a !global domain, the settings
are translated to ratios by scaling them against globally available
memory. dirty_throttle_control->gdtc is added to enable this when
CONFIG_CGROUP_WRITEBACK.global_dirty_limits() is now a thin wrapper around
domain_dirty_limits() and balance_dirty_pages() is updated to use the
new function too.This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Currently __wb_writeout_inc() and hard_dirty_limit() assume
global_wb_domain; however, cgroup writeback support requires
considering per-memcg wb_domain too.This patch separates out domain-specific part of __wb_writeout_inc()
into wb_domain_writeout_inc() which takes wb_domain as a parameter and
adds the parameter to hard_dirty_limit(). This will allow these two
functions to handle per-memcg wb_domains.This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Currently all dirty throttle operations use global_wb_domain; however,
cgroup writeback support requires considering per-memcg wb_domain too.
This patch adds dirty_throttle_control->dom and updates functions
which are directly using globabl_wb_domain to use it instead.As this makes global_update_bandwidth() a misnomer, the function is
renamed to domain_update_bandwidth().This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
wb->completions measures the wb's proportional write bandwidth in
global_wb_domain and thus naturally tied to the wb_domain. This patch
adds dirty_throttle_control->wb_completions which is initialized to
wb->completions by GDTC_INIT() and updates __wb_dirty_limits() to use
it instead of dereferencing wb->completions directly.This will allow dirty_throttle_control to represent different
wb_domains and the matching wb completions.This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
wb_position_ratio() is used to calculate pos_ratio, which is used for
two purposes. wb_update_dirty_ratelimit() uses it to adjust
wb->[balanced_]dirty_ratelimit gradually and balance_dirty_pages() to
immediately adjust dirty_ratelimit right before applying it to
determine pause duration.While wb_update_dirty_ratelimit() is separately rate limited from
balance_dirty_pages(), on the run where the ratelimit is updated, we
end up calculating pos_ratio twice with the same parameters.This patch adds dirty_throttle_control->pos_ratio.
balance_dirty_pages() calculates it once per run and
wb_update_dirty_ratelimit() uses the value stored in
dirty_throttle_control.This removes the duplicate calculation and also will help implementing
memcg wb_domain.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
wb_calc_thresh() calculates wb_thresh by scaling thresh according to
the wb's portion in the system-wide write bandwidth. cgroup writeback
support would need to calculate wb_thresh against memcg domain too.
This patch renames wb_calc_thresh() to __wb_calc_thresh() and makes it
take dirty_throttle_control so that the function can later be updated
to calculate against different domains according to
dirty_throttle_control.wb_calc_thresh() is now a thin wrapper around __wb_calc_thresh().
v2: The original version was incorrectly scaling dtc->dirty instead of
dtc->thresh. This was due to the extremely confusing function and
variable names. Added a rename patch and fixed this one.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
wb_bg_thresh is currently treated as a second-class citizen. It's
only used when BDI_CAP_STRICTLIMIT is set and balance_dirty_pages()
doesn't calculate it unless the cap is set. When the cap is set, the
calculated value is not passed around but instead recalculated
whenever it's used.wb_position_ratio() calculates it by scaling wb_thresh proportional to
bg_thresh / thresh. wb_update_dirty_ratelimit() uses wb_dirty_limit()
on bg_thresh, which should generally lead to a similar result as the
proportional scaling but can also be way off in the presence of
max/min_ratio settings.Avoiding wb_bg_thresh calculation saves us one u64 multiplication and
divsion when BDI_CAP_STRICTLIMIT is not set. Given that
balance_dirty_pages() is already ratelimited, this doesn't justify the
incurred extra complexity.This patch adds wb_bg_thresh to dirty_throttle_control and makes
wb_dirty_limits() always calculate it and updates the users to use the
pre-calculated value.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Dirty throttling implemented in balance_dirty_pages() and its
subroutines makes use of a number of parameters which are passed
around individually. This renders these functions somewhat unwieldy
and makes it difficult to add or change the involved parameters. Also
some functions use different or conflicting naming schemes for the
same parameters making the code confusing to follow.This patch consolidates the main parameters into struct
dirty_throttle_control so that they can be passed around easily and
adding new paramters isn't painful. This also unifies how a given
parameter is named and accessed. The drawback of using this type of
control structure rather than explicit paramters is that it isn't
immediately obvious which function accesses and modifies what;
however, it's fairly clear that the benefits outweigh in this case.GDTC_INIT() macro is provided to ease initializing
dirty_throttle_control for the global_wb_domain and
balance_dirty_pages() uses a separate pointer to point to its global
dirty_throttle_control. This is to make it uniform with memcg domain
handling which will be added later.This patch doesn't introduce any behavioral changes.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
This patch is a part of the series to define wb_domain which
represents a domain that wb's (bdi_writeback's) belong to and are
measured against each other in. This will enable IO backpressure
propagation for cgroup writeback.global_dirty_limit exists to regulate the global dirty threshold which
is a property of the wb_domain. This patch moves hard_dirty_limit,
dirty_lock, and update_time into wb_domain.This is pure reorganization and doesn't introduce any behavioral
changes.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
Dirtyable memory is distributed to a wb (bdi_writeback) according to
the relative bandwidth the wb is writing out in the whole system.
This distribution is global - each wb is measured against all other
wb's and gets the proportinately sized portion of the memory in the
whole system.For cgroup writeback, the amount of dirtyable memory is scoped by
memcg and thus each wb would need to be measured and controlled in its
memcg. IOW, a wb will belong to two writeback domains - the global
and memcg domains.Currently, what constitutes the global writeback domain are scattered
across a number of global states. This patch starts collecting them
into struct wb_domain.* fprop_global which serves as the basis for proportional bandwidth
measurement and its period timer are moved into struct wb_domain.* global_wb_domain hosts the states for the global domain.
* While at it, flatten wb_writeout_fraction() into its callers. This
thin wrapper doesn't provide any actual benefits while getting in
the way.This is pure reorganization and doesn't introduce any behavioral
changes.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
__wb_update_bandwidth() is called from two places -
fs/fs-writeback.c::balance_dirty_pages() and
mm/page-writeback.c::wb_writeback(). The latter updates only the
write bandwidth while the former also deals with the dirty ratelimit.
The two callsites are distinguished by whether @thresh parameter is
zero or not, which is cryptic. In addition, the two files define
their own different versions of wb_update_bandwidth() on top of
__wb_update_bandwidth(), which is confusing to say the least. This
patch cleans up [__]wb_update_bandwidth() in the following ways.* __wb_update_bandwidth() now takes explicit @update_ratelimit
parameter to gate dirty ratelimit handling.* mm/page-writeback.c::wb_update_bandwidth() is flattened into its
caller - balance_dirty_pages().* fs/fs-writeback.c::wb_update_bandwidth() is moved to
mm/page-writeback.c and __wb_update_bandwidth() is made static.* While at it, add a lockdep assertion to __wb_update_bandwidth().
Except for the lockdep addition, this is pure reorganization and
doesn't introduce any behavioral changes.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
The function name wb_dirty_limit(), its argument @dirty and the local
variable @wb_dirty are mortally confusing given that the function
calculates per-wb threshold value not dirty pages, especially given
that @dirty and @wb_dirty are used elsewhere for dirty pages.Let's rename the function to wb_calc_thresh() and wb_dirty to
wb_thresh.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Cc: Wu Fengguang
Cc: Greg Thelen
Signed-off-by: Jens Axboe -
bdi_start_background_writeback() currently takes @bdi and kicks the
root wb (bdi_writeback). In preparation for cgroup writeback support,
make it take wb instead.This patch doesn't make any functional difference.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
writeback_in_progress() currently takes @bdi and returns whether
writeback is in progress on its root wb (bdi_writeback). In
preparation for cgroup writeback support, make it take wb instead.
While at it, make it an inline function.This patch doesn't make any functional difference.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
For cgroup writeback support, all bdi-wide operations should be
distributed to all its wb's (bdi_writeback's).This patch updates laptop_mode_timer_fn() so that it invokes
wb_start_writeback() on all wb's rather than just the root one. As
the intent is writing out all dirty data, there's no reason to split
the number of pages to write.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
bdi_start_writeback() is a thin wrapper on top of
__wb_start_writeback() which is used only by laptop_mode_timer_fn().
This patches removes bdi_start_writeback(), renames
__wb_start_writeback() to wb_start_writeback() and makes
laptop_mode_timer_fn() use it instead.This doesn't cause any functional difference and will ease making
laptop_mode_timer_fn() cgroup writeback aware.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
bdi->min/max_ratio are user-configurable per-bdi knobs which regulate
dirty limit of each bdi. For cgroup writeback, they need to be
further distributed across wb's (bdi_writeback's) belonging to the
configured bdi.This patch introduces wb_min_max_ratio() which distributes
bdi->min/max_ratio according to a wb's proportion in the total active
bandwidth of its bdi.v2: Update wb_min_max_ratio() to fix a bug where both min and max were
assigned the min value and avoid calculations when possible.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
bdi_has_dirty_io() used to only reflect whether the root wb
(bdi_writeback) has dirty inodes. For cgroup writeback support, it
needs to take all active wb's into account. If any wb on the bdi has
dirty inodes, bdi_has_dirty_io() should return true.To achieve that, as inode_wb_list_{move|del}_locked() now keep track
of the dirty state transition of each wb, the number of dirty wbs can
be counted in the bdi; however, bdi is already aggregating
wb->avg_write_bandwidth which can easily be guaranteed to be > 0 when
there are any dirty inodes by ensuring wb->avg_write_bandwidth can't
dip below 1. bdi_has_dirty_io() can simply test whether
bdi->tot_write_bandwidth is zero or not.While this bumps the value of wb->avg_write_bandwidth to one when it
used to be zero, this shouldn't cause any meaningful behavior
difference.bdi_has_dirty_io() is made an inline function which tests whether
->tot_write_bandwidth is non-zero. Also, WARN_ON_ONCE()'s on its
value are added to inode_wb_list_{move|del}_locked().Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
cgroup writeback support needs to keep track of the sum of
avg_write_bandwidth of all wb's (bdi_writeback's) with dirty inodes to
distribute write workload. This patch adds bdi->tot_write_bandwidth
and updates inode_wb_list_move_locked(), inode_wb_list_del_locked()
and wb_update_write_bandwidth() to adjust it as wb's gain and lose
dirty inodes and its avg_write_bandwidth gets updated.As the update events are not synchronized with each other,
bdi->tot_write_bandwidth is an atomic_long_t.Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
Currently, balance_dirty_pages() always work on bdi->wb. This patch
updates it to work on the wb (bdi_writeback) matching memcg and blkcg
of the current task as that's what the inode is being dirtied against.balance_dirty_pages_ratelimited() now pins the current wb and passes
it to balance_dirty_pages().As no filesystem has FS_CGROUP_WRITEBACK yet, this doesn't lead to
visible behavior differences.v2: Updated for per-inode wb association.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
Until now, all WB_* stats were accounted against the root wb
(bdi_writeback), now that multiple wb (bdi_writeback) support is in
place, let's attributes the stats to the respective per-cgroup wb's.As no filesystem has FS_CGROUP_WRITEBACK yet, this doesn't lead to
visible behavior differences.v2: Updated for per-inode wb association.
Signed-off-by: Tejun Heo
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
For the planned cgroup writeback support, on each bdi
(backing_dev_info), each memcg will be served by a separate wb
(bdi_writeback). This patch updates bdi so that a bdi can host
multiple wbs (bdi_writebacks).On the default hierarchy, blkcg implicitly enables memcg. This allows
using memcg's page ownership for attributing writeback IOs, and every
memcg - blkcg combination can be served by its own wb by assigning a
dedicated wb to each memcg. This means that there may be multiple
wb's of a bdi mapped to the same blkcg. As congested state is per
blkcg - bdi combination, those wb's should share the same congested
state. This is achieved by tracking congested state via
bdi_writeback_congested structs which are keyed by blkcg.bdi->wb remains unchanged and will keep serving the root cgroup.
cgwb's (cgroup wb's) for non-root cgroups are created on-demand or
looked up while dirtying an inode according to the memcg of the page
being dirtied or current task. Each cgwb is indexed on bdi->cgwb_tree
by its memcg id. Once an inode is associated with its wb, it can be
retrieved using inode_to_wb().Currently, none of the filesystems has FS_CGROUP_WRITEBACK and all
pages will keep being associated with bdi->wb.v3: inode_attach_wb() in account_page_dirtied() moved inside
mapping_cap_account_dirty() block where it's known to be !NULL.
Also, an unnecessary NULL check before kfree() removed. Both
detected by the kbuild bot.v2: Updated so that wb association is per inode and wb is per memcg
rather than blkcg.Signed-off-by: Tejun Heo
Cc: kbuild test robot
Cc: Dan Carpenter
Cc: Jens Axboe
Cc: Jan Kara
Signed-off-by: Jens Axboe -
Writeback operations will now be per wb (bdi_writeback) instead of
bdi. Replace the relevant bdi references in symbol names and comments
with wb. This patch is purely cosmetic and doesn't make any
functional changes.Signed-off-by: Tejun Heo
Reviewed-by: Jan Kara
Cc: Wu Fengguang
Cc: Jens Axboe
Signed-off-by: Jens Axboe -
Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear. For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi. To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.This patch moves bandwidth related fields from backing_dev_info into
bdi_writeback.* The moved fields are: bw_time_stamp, dirtied_stamp, written_stamp,
write_bandwidth, avg_write_bandwidth, dirty_ratelimit,
balanced_dirty_ratelimit, completions and dirty_exceeded.* writeback_chunk_size() and over_bground_thresh() now take @wb
instead of @bdi.* bdi_writeout_fraction(bdi, ...) -> wb_writeout_fraction(wb, ...)
bdi_dirty_limit(bdi, ...) -> wb_dirty_limit(wb, ...)
bdi_position_ration(bdi, ...) -> wb_position_ratio(wb, ...)
bdi_update_writebandwidth(bdi, ...) -> wb_update_write_bandwidth(wb, ...)
[__]bdi_update_bandwidth(bdi, ...) -> [__]wb_update_bandwidth(wb, ...)
bdi_{max|min}_pause(bdi, ...) -> wb_{max|min}_pause(wb, ...)
bdi_dirty_limits(bdi, ...) -> wb_dirty_limits(wb, ...)* Init/exits of the relocated fields are moved to bdi_wb_init/exit()
respectively. Note that explicit zeroing is dropped in the process
as wb's are cleared in entirety anyway.* As there's still only one bdi_writeback per backing_dev_info, all
uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
introducing no behavior changes.v2: Typo in description fixed as suggested by Jan.
Signed-off-by: Tejun Heo
Reviewed-by: Jan Kara
Cc: Jens Axboe
Cc: Wu Fengguang
Cc: Jaegeuk Kim
Cc: Steven Whitehouse
Signed-off-by: Jens Axboe -
Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear. For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi. To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.This patch moves bdi->bdi_stat[] into wb.
* enum bdi_stat_item is renamed to wb_stat_item and the prefix of all
enums is changed from BDI_ to WB_.* BDI_STAT_BATCH() -> WB_STAT_BATCH()
* [__]{add|inc|dec|sum}_wb_stat(bdi, ...) -> [__]{add|inc}_wb_stat(wb, ...)
* bdi_stat[_error]() -> wb_stat[_error]()
* bdi_writeout_inc() -> wb_writeout_inc()
* stat init is moved to bdi_wb_init() and bdi_wb_exit() is added and
frees stat.* As there's still only one bdi_writeback per backing_dev_info, all
uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
introducing no behavior changes.Signed-off-by: Tejun Heo
Reviewed-by: Jan Kara
Cc: Jens Axboe
Cc: Wu Fengguang
Cc: Miklos Szeredi
Cc: Trond Myklebust
Signed-off-by: Jens Axboe -
When modifying PG_Dirty on cached file pages, update the new
MEM_CGROUP_STAT_DIRTY counter. This is done in the same places where
global NR_FILE_DIRTY is managed. The new memcg stat is visible in the
per memcg memory.stat cgroupfs file. The most recent past attempt at
this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632The new accounting supports future efforts to add per cgroup dirty
page throttling and writeback. It also helps an administrator break
down a container's memory usage and provides evidence to understand
memcg oom kills (the new dirty count is included in memcg oom kill
messages).The ability to move page accounting between memcg
(memory.move_charge_at_immigrate) makes this accounting more
complicated than the global counter. The existing
mem_cgroup_{begin,end}_page_stat() lock is used to serialize move
accounting with stat updates.
Typical update operation:
memcg = mem_cgroup_begin_page_stat(page)
if (TestSetPageDirty()) {
[...]
mem_cgroup_update_page_stat(memcg)
}
mem_cgroup_end_page_stat(memcg)Summary of mem_cgroup_end_page_stat() overhead:
- Without CONFIG_MEMCG it's a no-op
- With CONFIG_MEMCG and no inter memcg task movement, it's just
rcu_read_lock()
- With CONFIG_MEMCG and inter memcg task movement, it's
rcu_read_lock() + spin_lock_irqsave()A memcg parameter is added to several routines because their callers
now grab mem_cgroup_begin_page_stat() which returns the memcg later
needed by for mem_cgroup_update_page_stat().Because mem_cgroup_begin_page_stat() may disable interrupts, some
adjustments are needed:
- move __mark_inode_dirty() from __set_page_dirty() to its caller.
__mark_inode_dirty() locking does not want interrupts disabled.
- use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in
__delete_from_page_cache(), replace_page_cache_page(),
invalidate_complete_page2(), and __remove_mapping().text data bss dec hex filename
8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before
8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after
+192 text bytes
8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before
8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after
+773 text bytesPerformance tests run on v4.0-rc1-36-g4f671fe2f952. Lower is better for
all metrics, they're all wall clock or cycle counts. The read and write
fault benchmarks just measure fault time, they do not include I/O time.* CONFIG_MEMCG not set:
baseline patched
kbuild 1m25.030000(+-0.088% 3 samples) 1m25.426667(+-0.120% 3 samples)
dd write 100 MiB 0.859211561 +-15.10% 0.874162885 +-15.03%
dd write 200 MiB 1.670653105 +-17.87% 1.669384764 +-11.99%
dd write 1000 MiB 8.434691190 +-14.15% 8.474733215 +-14.77%
read fault cycles 254.0(+-0.000% 10 samples) 253.0(+-0.000% 10 samples)
write fault cycles 2021.2(+-3.070% 10 samples) 1984.5(+-1.036% 10 samples)* CONFIG_MEMCG=y root_memcg:
baseline patched
kbuild 1m25.716667(+-0.105% 3 samples) 1m25.686667(+-0.153% 3 samples)
dd write 100 MiB 0.855650830 +-14.90% 0.887557919 +-14.90%
dd write 200 MiB 1.688322953 +-12.72% 1.667682724 +-13.33%
dd write 1000 MiB 8.418601605 +-14.30% 8.673532299 +-15.00%
read fault cycles 266.0(+-0.000% 10 samples) 266.0(+-0.000% 10 samples)
write fault cycles 2051.7(+-1.349% 10 samples) 2049.6(+-1.686% 10 samples)* CONFIG_MEMCG=y non-root_memcg:
baseline patched
kbuild 1m26.120000(+-0.273% 3 samples) 1m25.763333(+-0.127% 3 samples)
dd write 100 MiB 0.861723964 +-15.25% 0.818129350 +-14.82%
dd write 200 MiB 1.669887569 +-13.30% 1.698645885 +-13.27%
dd write 1000 MiB 8.383191730 +-14.65% 8.351742280 +-14.52%
read fault cycles 265.7(+-0.172% 10 samples) 267.0(+-0.000% 10 samples)
write fault cycles 2070.6(+-1.512% 10 samples) 2084.4(+-2.148% 10 samples)As expected anon page faults are not affected by this patch.
tj: Updated to apply on top of the recent cancel_dirty_page() changes.
Signed-off-by: Sha Zhengju
Signed-off-by: Greg Thelen
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe
