04 Dec, 2015
12 commits
-
In an overcommitted guest where some vCPUs have to be halted to make
forward progress in other areas, it is highly likely that a vCPU later
in the spinlock queue will be spinning while the ones earlier in the
queue would have been halted. The spinning in the later vCPUs is then
just a waste of precious CPU cycles because they are not going to
get the lock soon as the earlier ones have to be woken up and take
their turn to get the lock.This patch implements an adaptive spinning mechanism where the vCPU
will call pv_wait() if the previous vCPU is not running.Linux kernel builds were run in KVM guest on an 8-socket, 4
cores/socket Westmere-EX system and a 4-socket, 8 cores/socket
Haswell-EX system. Both systems are configured to have 32 physical
CPUs. The kernel build times before and after the patch were:Westmere Haswell
Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs
----- -------- -------- -------- --------
Before patch 3m02.3s 5m00.2s 1m43.7s 3m03.5s
After patch 3m03.0s 4m37.5s 1m43.0s 2m47.2sFor 32 vCPUs, this patch doesn't cause any noticeable change in
performance. For 48 vCPUs (over-committed), there is about 8%
performance improvement.Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-8-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
This patch allows one attempt for the lock waiter to steal the lock
when entering the PV slowpath. To prevent lock starvation, the pending
bit will be set by the queue head vCPU when it is in the active lock
spinning loop to disable any lock stealing attempt. This helps to
reduce the performance penalty caused by lock waiter preemption while
not having much of the downsides of a real unfair lock.The pv_wait_head() function was renamed as pv_wait_head_or_lock()
as it was modified to acquire the lock before returning. This is
necessary because of possible lock stealing attempts from other tasks.Linux kernel builds were run in KVM guest on an 8-socket, 4
cores/socket Westmere-EX system and a 4-socket, 8 cores/socket
Haswell-EX system. Both systems are configured to have 32 physical
CPUs. The kernel build times before and after the patch were:Westmere Haswell
Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs
----- -------- -------- -------- --------
Before patch 3m15.6s 10m56.1s 1m44.1s 5m29.1s
After patch 3m02.3s 5m00.2s 1m43.7s 3m03.5sFor the overcommited case (48 vCPUs), this patch is able to reduce
kernel build time by more than 54% for Westmere and 44% for Haswell.Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447190336-53317-1-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
This patch enables the accumulation of kicking and waiting related
PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration
option is selected. It also enables the collection of data which
enable us to calculate the kicking and wakeup latencies which have
a heavy dependency on the CPUs being used.The statistical counters are per-cpu variables to minimize the
performance overhead in their updates. These counters are exported
via the debugfs filesystem under the qlockstat directory. When the
corresponding debugfs files are read, summation and computing of the
required data are then performed.The measured latencies for different CPUs are:
CPU Wakeup Kicking
--- ------ -------
Haswell-EX 63.6us 7.4us
Westmere-EX 67.6us 9.3usThe measured latencies varied a bit from run-to-run. The wakeup
latency is much higher than the kicking latency.A sample of statistical counters after system bootup (with vCPU
overcommit) was:pv_hash_hops=1.00
pv_kick_unlock=1148
pv_kick_wake=1146
pv_latency_kick=11040
pv_latency_wake=194840
pv_spurious_wakeup=7
pv_wait_again=4
pv_wait_head=23
pv_wait_node=1129Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-6-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
These are some notes on the scheduler locking and how it provides
program order guarantees on SMP systems.( This commit is in the locking tree, because the new documentation
refers to a newly introduced locking primitive. )Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Boqun Feng
Cc: David Howells
Cc: Jonathan Corbet
Cc: Linus Torvalds
Cc: Michal Hocko
Cc: Mike Galbraith
Cc: Oleg Nesterov
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: Will Deacon
Signed-off-by: Ingo Molnar -
Introduce smp_cond_acquire() which combines a control dependency and a
read barrier to form acquire semantics.This primitive has two benefits:
- it documents control dependencies,
- its typically cheaper than using smp_load_acquire() in a loop.Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
So we want to change a locking API, but the scheduler uses it, and a conflict
is generated by a recent scheduler fix.Pick up the pending scheduler fixes to make life easier.
Signed-off-by: Ingo Molnar
-
Oleg noticed that its possible to falsely observe p->on_cpu == 0 such
that we'll prematurely continue with the wakeup and effectively run p on
two CPUs at the same time.Even though the overlap is very limited; the task is in the middle of
being scheduled out; it could still result in corruption of the
scheduler data structures.CPU0 CPU1
set_current_state(...)
context_switch(X, Y)
prepare_lock_switch(Y)
Y->on_cpu = 1;
finish_lock_switch(X)
store_release(X->on_cpu, 0);try_to_wake_up(X)
LOCK(p->pi_lock);t = X->on_cpu; // 0
context_switch(Y, X)
prepare_lock_switch(X)
X->on_cpu = 1;
finish_lock_switch(Y)
store_release(Y->on_cpu, 0);
schedule();
deactivate_task(X);
X->on_rq = 0;if (X->on_rq) // false
if (t) while (X->on_cpu)
cpu_relax();context_switch(X, ..)
finish_lock_switch(X)
store_release(X->on_cpu, 0);Avoid the load of X->on_cpu being hoisted over the X->on_rq load.
Reported-by: Oleg Nesterov
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
Explain how the control dependency and smp_rmb() end up providing
ACQUIRE semantics and pair with smp_store_release() in
finish_lock_switch().Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Oleg Nesterov
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
/proc/stats shows invalid gtime when the thread is running in guest.
When vtime accounting is not enabled, we cannot get a valid delta.
The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap
is only updated when vtime accounting is runtime enabled.This patch makes task_gtime() just return gtime without computing the
buggy non-existing tickless delta when vtime accounting is not enabled.Use context_tracking_is_enabled() to check if vtime is accounting on
some cpu, in which case only we need to check the tickless delta. This
way we fix the gtime value regression on machines not running nohz full.The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and
CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full.I ran and stop a busy loop in VM and see the gtime in host.
Dump the 43rd field which shows the gtime in every second:# while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done
S 4348
R 7064566
R 7064766
R 7064967
R 7065168
S 4759
S 4759During running busy loop, it returns large value.
After applying this patch, we can see right gtime.
# while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done
S 5338
R 5365
R 5465
R 5566
R 5666
S 5726
S 5726Signed-off-by: Hiroshi Shimamoto
Signed-off-by: Frederic Weisbecker
Signed-off-by: Peter Zijlstra (Intel)
Cc: Chris Metcalf
Cc: Christoph Lameter
Cc: Linus Torvalds
Cc: Luiz Capitulino
Cc: Mike Galbraith
Cc: Paul E . McKenney
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Rik van Riel
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar -
root_domain::rto_mask allocated through alloc_cpumask_var()
contains garbage data, this may cause problems. For instance,
When doing pull_rt_task(), it may do useless iterations if
rto_mask retains some extra garbage bits. Worse still, this
violates the isolated domain rule for clustered scheduling
using cpuset, because the tasks(with all the cpus allowed)
belongs to one root domain can be pulled away into another
root domain.The patch cleans the garbage by using zalloc_cpumask_var()
instead of alloc_cpumask_var() for root_domain::rto_mask
allocation, thereby addressing the issues.Do the same thing for root_domain's other cpumask memembers:
dlo_mask, span, and online.Signed-off-by: Xunlei Pang
Signed-off-by: Peter Zijlstra (Intel)
Cc:
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1449057179-29321-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar -
Because wakeups can (fundamentally) be late, a task might not be in
the expected state. Therefore testing against a task's state is racy,
and can yield false positives.Signed-off-by: Sasha Levin
Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: oleg@redhat.com
Fixes: 9067ac85d533 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task")
Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.com
Signed-off-by: Ingo Molnar -
Vladimir reported getting RCU stall warnings and bisected it back to
commit:743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")
That commit inadvertently reversed the calls to schedule() and signal_pending(),
thereby not handling the case where the signal receives while we sleep.Reported-by: Vladimir Murzin
Tested-by: Vladimir Murzin
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: mark.rutland@arm.com
Cc: neilb@suse.de
Cc: oleg@redhat.com
Fixes: 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")
Fixes: cbbce8220949 ("SCHED: add some "wait..on_bit...timeout()" interfaces.")
Link: http://lkml.kernel.org/r/20151201130404.GL3816@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar
23 Nov, 2015
20 commits
-
The unlock function in queued spinlocks was optimized for better
performance on bare metal systems at the expense of virtualized guests.For x86-64 systems, the unlock call needs to go through a
PV_CALLEE_SAVE_REGS_THUNK() which saves and restores 8 64-bit
registers before calling the real __pv_queued_spin_unlock()
function. The thunk code may also be in a separate cacheline from
__pv_queued_spin_unlock().This patch optimizes the PV unlock code path by:
1) Moving the unlock slowpath code from the fastpath into a separate
__pv_queued_spin_unlock_slowpath() function to make the fastpath
as simple as possible..2) For x86-64, hand-coded an assembly function to combine the register
saving thunk code with the fastpath code. Only registers that
are used in the fastpath will be saved and restored. If the
fastpath fails, the slowpath function will be called via another
PV_CALLEE_SAVE_REGS_THUNK(). For 32-bit, it falls back to the C
__pv_queued_spin_unlock() code as the thunk saves and restores
only one 32-bit register.With a microbenchmark of 5M lock-unlock loop, the table below shows
the execution times before and after the patch with different number
of threads in a VM running on a 32-core Westmere-EX box with x86-64
4.2-rc1 based kernels:Threads Before patch After patch % Change
------- ------------ ----------- --------
1 134.1 ms 119.3 ms -11%
2 1286 ms 953 ms -26%
3 3715 ms 3480 ms -6.3%
4 4092 ms 3764 ms -8.0%Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-5-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
With optimistic prefetch of the next node cacheline, the next pointer
may have been properly inititalized. As a result, the reading
of node->next in the contended path may be redundant. This patch
eliminates the redundant read if the next pointer value is not NULL.Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-4-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
A queue head CPU, after acquiring the lock, will have to notify
the next CPU in the wait queue that it has became the new queue
head. This involves loading a new cacheline from the MCS node of the
next CPU. That operation can be expensive and add to the latency of
locking operation.This patch addes code to optmistically prefetch the next MCS node
cacheline if the next pointer is defined and it has been spinning
for the MCS lock for a while. This reduces the locking latency and
improves the system throughput.The performance change will depend on whether the prefetch overhead
can be hidden within the latency of the lock spin loop. On really
short critical section, there may not be performance gain at all. With
longer critical section, however, it was found to have a performance
boost of 5-10% over a range of different queue depths with a spinlock
loop microbenchmark.Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-3-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
This patch replaces the cmpxchg() and xchg() calls in the native
qspinlock code with the more relaxed _acquire or _release versions of
those calls to enable other architectures to adopt queued spinlocks
with less memory barrier performance overhead.Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Scott J Norton
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/1447114167-47185-2-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar -
Some atomic operations now have _relaxed/acquire/release variants, this
patch adds some trivial tests for two purposes:1. test the behavior of these new operations in single-CPU
environment.2. make their code generated before we actually use them somewhere,
so that we can examine their assembly code.Signed-off-by: Boqun Feng
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Davidlohr Bueso
Cc: Linus Torvalds
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: Waiman Long
Cc: Will Deacon
Link: http://lkml.kernel.org/r/1446634365-25176-1-git-send-email-boqun.feng@gmail.com
Signed-off-by: Ingo Molnar -
The push_irq_work_func() function is conditionally defined only
when both CONFIG_SMP and HAVE_RT_PUSH_IPI are defined, but the
forward declaration remains visibile without HAVE_RT_PUSH_IPI,
causing a gcc warning in ARM64 allnoconfig:kernel/sched/rt.c:68:13: warning: 'push_irq_work_func' declared 'static' but never defined [-Wunused-function]
This changes the code to use the same condition for both the
declaration and the function definition, which gets rid of the
warning.As Peter Zijlstra, we can possibly get rid of the whole HAVE_RT_PUSH_IPI
thing after:8053871d0f7f ("smp: Fix smp_call_function_single_async() locking")
Until that is done, this patch can be used to avoid the warning.
Signed-off-by: Arnd Bergmann
Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Steven Rostedt
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Fixes: b6366f048e0c ("sched/rt: Use IPI to trigger RT task push migration instead of pulling")
Link: http://lkml.kernel.org/r/3828565.oKfGk7yNIT@wuerfel
Signed-off-by: Ingo Molnar -
Merge slub bulk allocator updates from Andrew Morton:
"This missed the merge window because I was waiting for some repairs to
come in. Nothing actually uses the bulk allocator yet and the changes
to other code paths are pretty small. And the net guys are waiting
for this so they can start merging the client code"More comments from Jesper Dangaard Brouer:
"The kmem_cache_alloc_bulk() call, in mm/slub.c, were included in
previous kernel. The present version contains a bug. Vladimir
Davydov noticed it contained a bug, when kernel is compiled with
CONFIG_MEMCG_KMEM (see commit 03ec0ed57ffc: "slub: fix kmem cgroup
bug in kmem_cache_alloc_bulk"). Plus the mem cgroup counterpart in
kmem_cache_free_bulk() were missing (see commit 033745189b1b "slub:
add missing kmem cgroup support to kmem_cache_free_bulk").I don't consider the fix stable-material because there are no in-tree
users of the API.But with known bugs (for memcg) I cannot start using the API in the
net-tree"* emailed patches from Andrew Morton :
slab/slub: adjust kmem_cache_alloc_bulk API
slub: add missing kmem cgroup support to kmem_cache_free_bulk
slub: fix kmem cgroup bug in kmem_cache_alloc_bulk
slub: optimize bulk slowpath free by detached freelist
slub: support for bulk free with SLUB freelists -
Pull tty/serial fixes from Greg KH:
"Here are a few small tty/serial driver fixes for 4.4-rc2 that resolve
some reported problems.All have been in linux-next, full details are in the shortlog below"
* tag 'tty-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
serial: export fsl8250_handle_irq
serial: 8250_mid: Add missing dependency
tty: audit: Fix audit source
serial: etraxfs-uart: Fix crash
serial: fsl_lpuart: Fix earlycon support
bcm63xx_uart: Use the device name when registering an interrupt
tty: Fix direct use of tty buffer work
tty: Fix tty_send_xchar() lock order inversion -
Pull staging/IIO fixes from Greg KH:
"Here are some staging and iio driver fixes for 4.4-rc2. All of these
are in response to issues that have been reported and have been in
linux-next for a while"* tag 'staging-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
Revert "Staging: wilc1000: coreconfigurator: Drop unneeded wrapper functions"
iio: adc: xilinx: Fix VREFN scale
iio: si7020: Swap data byte order
iio: adc: vf610_adc: Fix division by zero error
iio:ad7793: Fix ad7785 product ID
iio: ad5064: Fix ad5629/ad5669 shift
iio:ad5064: Make sure ad5064_i2c_write() returns 0 on success
iio: lpc32xx_adc: fix warnings caused by enabling unprepared clock
staging: iio: select IRQ_WORK for IIO_DUMMY_EVGEN
vf610_adc: Fix internal temperature calculation -
Pull USB fixes from Greg KH:
"Here are a number of USB fixes and new device ids for 4.4-rc2. All
have been in linux-next and the details are in the shortlog"* tag 'usb-4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (28 commits)
usblp: do not set TASK_INTERRUPTIBLE before lock
USB: MAINTAINERS: cxacru
usb: kconfig: fix warning of select USB_OTG
USB: option: add XS Stick W100-2 from 4G Systems
xhci: Fix a race in usb2 LPM resume, blocking U3 for usb2 devices
usb: xhci: fix checking ep busy for CFC
xhci: Workaround to get Intel xHCI reset working more reliably
usb: chipidea: imx: fix a possible NULL dereference
usb: chipidea: usbmisc_imx: fix a possible NULL dereference
usb: chipidea: otg: gadget module load and unload support
usb: chipidea: debug: disable usb irq while role switch
ARM: dts: imx27.dtsi: change the clock information for usb
usb: chipidea: imx: refine clock operations to adapt for all platforms
usb: gadget: atmel_usba_udc: Expose correct device speed
usb: musb: enable usb_dma parameter
usb: phy: phy-mxs-usb: fix a possible NULL dereference
usb: dwc3: gadget: let us set lower max_speed
usb: musb: fix tx fifo flush handling
usb: gadget: f_loopback: fix the warning during the enumeration
usb: dwc2: host: Fix remote wakeup when not in DWC2_L2
... -
Pull MIPS fixes from Ralf Baechle:
- Fix a flood of annoying build warnings
- A number of fixes for Atheros 79xx platforms
* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
MIPS: ath79: Add a machine entry for booting OF machines
MIPS: ath79: Fix the size of the MISC INTC registers in ar9132.dtsi
MIPS: ath79: Fix the DDR control initialization on ar71xx and ar934x
MIPS: Fix flood of warnings about comparsion being always true. -
Pull parisc update from Helge Deller:
"This patchset adds Huge Page and HUGETLBFS support for parisc"Honestly, the hugepage support should have gone through in the merge
window, and is not really an rc-time fix. But it only touches
arch/parisc, and I cannot find it in myself to care. If one of the
three parisc users notices a breakage, I will point at Helge and make
rude farting noises.* 'parisc-4.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Map kernel text and data on huge pages
parisc: Add Huge Page and HUGETLBFS support
parisc: Use long branch to do_syscall_trace_exit
parisc: Increase initial kernel mapping to 32MB on 64bit kernel
parisc: Initialize the fault vector earlier in the boot process.
parisc: Add defines for Huge page support
parisc: Drop unused MADV_xxxK_PAGES flags from asm/mman.h
parisc: Drop definition of start_thread_som for HP-UX SOM binaries
parisc: Fix wrong comment regarding first pmd entry flags -
Pull perf tool fixes from Thomas Gleixner:
"A couple of fixes for perf tools:- Build system updates
- Plug a memory leak in an error path of perf probe
- Tear down probes correctly when adding fails
- Fixes to the perf symbol handling
- Fix ordering of event processing in buildid-list
- Fix per DSO filtering in the histogram browser"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf probe: Clear probe_trace_event when add_probe_trace_event() fails
perf probe: Fix memory leaking on failure by clearing all probe_trace_events
perf inject: Also re-pipe lost_samples event
perf buildid-list: Requires ordered events
perf symbols: Fix dso lookup by long name and missing buildids
perf symbols: Allow forcing reading of non-root owned files by root
perf hists browser: The dso can be obtained from popup_action->ms.map->dso
perf hists browser: Fix 'd' hotkey action to filter by DSO
perf symbols: Rebuild rbtree when adjusting symbols for kcore
tools: Add a "make all" rule
tools: Actually install tmon in the install rule -
Pull x86 fixes from Thomas Gleixner:
"This update contains:- MPX updates for handling 32bit processes
- A fix for a long standing bug in 32bit signal frame handling
related to FPU/XSAVE state- Handle get_xsave_addr() correctly in KVM
- Fix SMAP check under paravirtualization
- Add a comment to the static function trace entry to avoid further
confusion about the difference to dynamic tracing"* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/cpu: Fix SMAP check in PVOPS environments
x86/ftrace: Add comment on static function tracing
x86/fpu: Fix get_xsave_addr() behavior under virtualization
x86/fpu: Fix 32-bit signal frame handling
x86/mpx: Fix 32-bit address space calculation
x86/mpx: Do proper get_user() when running 32-bit binaries on 64-bit kernels -
Adjust kmem_cache_alloc_bulk API before we have any real users.
Adjust API to return type 'int' instead of previously type 'bool'. This
is done to allow future extension of the bulk alloc API.A future extension could be to allow SLUB to stop at a page boundary, when
specified by a flag, and then return the number of objects.The advantage of this approach, would make it easier to make bulk alloc
run without local IRQs disabled. With an approach of cmpxchg "stealing"
the entire c->freelist or page->freelist. To avoid overshooting we would
stop processing at a slab-page boundary. Else we always end up returning
some objects at the cost of another cmpxchg.To keep compatible with future users of this API linking against an older
kernel when using the new flag, we need to return the number of allocated
objects with this API change.Signed-off-by: Jesper Dangaard Brouer
Cc: Vladimir Davydov
Acked-by: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Initial implementation missed support for kmem cgroup support in
kmem_cache_free_bulk() call, add this.If CONFIG_MEMCG_KMEM is not enabled, the compiler should be smart enough
to not add any asm code.Incoming bulk free objects can belong to different kmem cgroups, and
object free call can happen at a later point outside memcg context. Thus,
we need to keep the orig kmem_cache, to correctly verify if a memcg object
match against its "root_cache" (s->memcg_params.root_cache).Signed-off-by: Jesper Dangaard Brouer
Reviewed-by: Vladimir Davydov
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The call slab_pre_alloc_hook() interacts with kmemgc and is not allowed to
be called several times inside the bulk alloc for loop, due to the call to
memcg_kmem_get_cache().This would result in hitting the VM_BUG_ON in __memcg_kmem_get_cache.
As suggested by Vladimir Davydov, change slab_post_alloc_hook() to be able
to handle an array of objects.A subtle detail is, loop iterator "i" in slab_post_alloc_hook() must have
same type (size_t) as size argument. This helps the compiler to easier
realize that it can remove the loop, when all debug statements inside loop
evaluates to nothing. Note, this is only an issue because the kernel is
compiled with GCC option: -fno-strict-overflowIn slab_alloc_node() the compiler inlines and optimizes the invocation of
slab_post_alloc_hook(s, flags, 1, &object) by removing the loop and access
object directly.Signed-off-by: Jesper Dangaard Brouer
Reported-by: Vladimir Davydov
Suggested-by: Vladimir Davydov
Reviewed-by: Vladimir Davydov
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This change focus on improving the speed of object freeing in the
"slowpath" of kmem_cache_free_bulk.The calls slab_free (fastpath) and __slab_free (slowpath) have been
extended with support for bulk free, which amortize the overhead of
the (locked) cmpxchg_double.To use the new bulking feature, we build what I call a detached
freelist. The detached freelist takes advantage of three properties:1) the free function call owns the object that is about to be freed,
thus writing into this memory is synchronization-free.2) many freelist's can co-exist side-by-side in the same slab-page
each with a separate head pointer.3) it is the visibility of the head pointer that needs synchronization.
Given these properties, the brilliant part is that the detached
freelist can be constructed without any need for synchronization. The
freelist is constructed directly in the page objects, without any
synchronization needed. The detached freelist is allocated on the
stack of the function call kmem_cache_free_bulk. Thus, the freelist
head pointer is not visible to other CPUs.All objects in a SLUB freelist must belong to the same slab-page.
Thus, constructing the detached freelist is about matching objects
that belong to the same slab-page. The bulk free array is scanned is
a progressive manor with a limited look-ahead facility.Kmem debug support is handled in call of slab_free().
Notice kmem_cache_free_bulk no longer need to disable IRQs. This
only slowed down single free bulk with approx 3 cycles.Performance data:
Benchmarked[1] obj size 256 bytes on CPU i7-4790K @ 4.00GHzSLUB fastpath single object quick reuse: 47 cycles(tsc) 11.931 ns
To get stable and comparable numbers, the kernel have been booted with
"slab_merge" (this also improve performance for larger bulk sizes).Performance data, compared against fallback bulking:
bulk - fallback bulk - improvement with this patch
1 - 62 cycles(tsc) 15.662 ns - 49 cycles(tsc) 12.407 ns- improved 21.0%
2 - 55 cycles(tsc) 13.935 ns - 30 cycles(tsc) 7.506 ns - improved 45.5%
3 - 53 cycles(tsc) 13.341 ns - 23 cycles(tsc) 5.865 ns - improved 56.6%
4 - 52 cycles(tsc) 13.081 ns - 20 cycles(tsc) 5.048 ns - improved 61.5%
8 - 50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.659 ns - improved 64.0%
16 - 49 cycles(tsc) 12.412 ns - 17 cycles(tsc) 4.495 ns - improved 65.3%
30 - 49 cycles(tsc) 12.484 ns - 18 cycles(tsc) 4.533 ns - improved 63.3%
32 - 50 cycles(tsc) 12.627 ns - 18 cycles(tsc) 4.707 ns - improved 64.0%
34 - 96 cycles(tsc) 24.243 ns - 23 cycles(tsc) 5.976 ns - improved 76.0%
48 - 83 cycles(tsc) 20.818 ns - 21 cycles(tsc) 5.329 ns - improved 74.7%
64 - 74 cycles(tsc) 18.700 ns - 20 cycles(tsc) 5.127 ns - improved 73.0%
128 - 90 cycles(tsc) 22.734 ns - 27 cycles(tsc) 6.833 ns - improved 70.0%
158 - 99 cycles(tsc) 24.776 ns - 30 cycles(tsc) 7.583 ns - improved 69.7%
250 - 104 cycles(tsc) 26.089 ns - 37 cycles(tsc) 9.280 ns - improved 64.4%Performance data, compared current in-kernel bulking:
bulk - curr in-kernel - improvement with this patch
1 - 46 cycles(tsc) - 49 cycles(tsc) - improved (cycles:-3) -6.5%
2 - 27 cycles(tsc) - 30 cycles(tsc) - improved (cycles:-3) -11.1%
3 - 21 cycles(tsc) - 23 cycles(tsc) - improved (cycles:-2) -9.5%
4 - 18 cycles(tsc) - 20 cycles(tsc) - improved (cycles:-2) -11.1%
8 - 17 cycles(tsc) - 18 cycles(tsc) - improved (cycles:-1) -5.9%
16 - 18 cycles(tsc) - 17 cycles(tsc) - improved (cycles: 1) 5.6%
30 - 18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0) 0.0%
32 - 18 cycles(tsc) - 18 cycles(tsc) - improved (cycles: 0) 0.0%
34 - 78 cycles(tsc) - 23 cycles(tsc) - improved (cycles:55) 70.5%
48 - 60 cycles(tsc) - 21 cycles(tsc) - improved (cycles:39) 65.0%
64 - 49 cycles(tsc) - 20 cycles(tsc) - improved (cycles:29) 59.2%
128 - 69 cycles(tsc) - 27 cycles(tsc) - improved (cycles:42) 60.9%
158 - 79 cycles(tsc) - 30 cycles(tsc) - improved (cycles:49) 62.0%
250 - 86 cycles(tsc) - 37 cycles(tsc) - improved (cycles:49) 57.0%Performance with normal SLUB merging is significantly slower for
larger bulking. This is believed to (primarily) be an effect of not
having to share the per-CPU data-structures, as tuning per-CPU size
can achieve similar performance.bulk - slab_nomerge - normal SLUB merge
1 - 49 cycles(tsc) - 49 cycles(tsc) - merge slower with cycles:0
2 - 30 cycles(tsc) - 30 cycles(tsc) - merge slower with cycles:0
3 - 23 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:0
4 - 20 cycles(tsc) - 20 cycles(tsc) - merge slower with cycles:0
8 - 18 cycles(tsc) - 18 cycles(tsc) - merge slower with cycles:0
16 - 17 cycles(tsc) - 17 cycles(tsc) - merge slower with cycles:0
30 - 18 cycles(tsc) - 23 cycles(tsc) - merge slower with cycles:5
32 - 18 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:4
34 - 23 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:-1
48 - 21 cycles(tsc) - 22 cycles(tsc) - merge slower with cycles:1
64 - 20 cycles(tsc) - 48 cycles(tsc) - merge slower with cycles:28
128 - 27 cycles(tsc) - 57 cycles(tsc) - merge slower with cycles:30
158 - 30 cycles(tsc) - 59 cycles(tsc) - merge slower with cycles:29
250 - 37 cycles(tsc) - 56 cycles(tsc) - merge slower with cycles:19Joint work with Alexander Duyck.
[1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/slab_bulk_test01.c
[akpm@linux-foundation.org: BUG_ON -> WARN_ON;return]
Signed-off-by: Jesper Dangaard Brouer
Signed-off-by: Alexander Duyck
Acked-by: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Make it possible to free a freelist with several objects by adjusting API
of slab_free() and __slab_free() to have head, tail and an objects counter
(cnt).Tail being NULL indicate single object free of head object. This allow
compiler inline constant propagation in slab_free() and
slab_free_freelist_hook() to avoid adding any overhead in case of single
object free.This allows a freelist with several objects (all within the same
slab-page) to be free'ed using a single locked cmpxchg_double in
__slab_free() and with an unlocked cmpxchg_double in slab_free().Object debugging on the free path is also extended to handle these
freelists. When CONFIG_SLUB_DEBUG is enabled it will also detect if
objects don't belong to the same slab-page.These changes are needed for the next patch to bulk free the detached
freelists it introduces and constructs.Micro benchmarking showed no performance reduction due to this change,
when debugging is turned off (compiled with CONFIG_SLUB_DEBUG).Signed-off-by: Jesper Dangaard Brouer
Signed-off-by: Alexander Duyck
Acked-by: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 Nov, 2015
8 commits
-
Adjust the linker script and map_pages() to map kernel text and data on
physical 1MB huge/large pages.Signed-off-by: Helge Deller
-
This patch adds huge page support to allow userspace to allocate huge
pages and to use hugetlbfs filesystem on 32- and 64-bit Linux kernels.
A later patch will add kernel support to map kernel text and data on
huge pages.The only requirement is, that the kernel needs to be compiled for a
PA8X00 CPU (PA2.0 architecture). Older PA1.X CPUs do not support
variable page sizes. 64bit Kernels are compiled for PA2.0 by default.Technically on parisc multiple physical huge pages may be needed to
emulate standard 2MB huge pages.Signed-off-by: Helge Deller
-
Use the 22bit instead of the 17bit branch instruction on a 64bit kernel
to reach the do_syscall_trace_exit function from the gateway page.
A huge page enabled kernel may need the additional branch distance bits.Signed-off-by: Helge Deller
-
For the 64bit kernel the initially 16 MB kernel memory might become too
small if you build a kernel with many modules built-in and with kernel
text and data areas mapped on huge pages.This patch increases the initial mapping to 32MB for 64bit kernels and
keeps 16MB for 32bit kernels.Signed-off-by: Helge Deller
-
A fault vector on parisc needs to be 2K aligned. Furthermore the
checksum of the fault vector needs to sum up to 0 which is being
calculated and written at runtime.Up to now we aligned both PA20 and PA11 fault vectors on the same 4K
page in order to easily write the checksum after having mapped the
kernel read-only (by mapping this page only as read-write).
But when we want to map the kernel text and data on huge pages this
makes things harder.
So, simplify it by aligning both fault vectors on 2K boundries and write
the checksum before we map the page read-only.Signed-off-by: Helge Deller
-
Huge pages on parisc will have the same size as one pmd table, which
is on a 64bit kernel 2MB on a kernel with 4K kernel page sizes, and
on a 32bit kernel 4MB when used with 4K kernel pages.Since parisc does not physically supports 2MB huge page sizes, emulate
it with two consecutive 1MB page sizes instead. Keeping the same huge
page size as one pmd will allow us to add transparent huge page support
later on.Bit 21 in the pte flags was unused and will now be used to mark a page
as huge page (_PAGE_HPAGE_BIT).Signed-off-by: Helge Deller
-
Drop the MADV_xxK_PAGES flags, which were never used and were from a proposed
API which was never integrated into the generic Linux kernel code.Cc: stable@vger.kernel.org
Signed-off-by: Helge Deller -
Merge misc fixes from Andrew Morton:
"A bunch of fixes"* emailed patches from Andrew Morton :
slub: mark the dangling ifdef #else of CONFIG_SLUB_DEBUG
slub: avoid irqoff/on in bulk allocation
slub: create new ___slab_alloc function that can be called with irqs disabled
mm: fix up sparse warning in gfpflags_allow_blocking
ocfs2: fix umask ignored issue
PM/OPP: add entry in MAINTAINERS
kernel/panic.c: turn off locks debug before releasing console lock
kernel/signal.c: unexport sigsuspend()
kasan: fix kmemleak false-positive in kasan_module_alloc()
fat: fix fake_offset handling on error path
mm/hugetlbfs: fix bugs in fallocate hole punch of areas with holes
mm/page-writeback.c: initialize m_dirty to avoid compile warning
various: fix pci_set_dma_mask return value checking
mm: loosen MADV_NOHUGEPAGE to enable Qemu postcopy on s390
mm: vmalloc: don't remove inexistent guard hole in remove_vm_area()
tools/vm/page-types.c: support KPF_IDLE
ncpfs: don't allow negative timeouts
configfs: allow dynamic group creation
MAINTAINERS: add Moritz as reviewer for FPGA Manager Framework
slab.h: sprinkle __assume_aligned attributes
