Eric Lee / linux-smarc-t335x-v3.2

18 Aug, 2010

17 commits

  • 6416ccb78   fs: scale files_lock ... Browse Code »

    fs: scale files_lock

    Improve scalability of files_lock by adding per-cpu, per-sb files lists,
    protected with an lglock. The lglock provides fast access to the per-cpu lists
    to add and remove files. It also provides a snapshot of all the per-cpu lists
    (although this is very slow).

    One difficulty with this approach is that a file can be removed from the list
    by another CPU. We must track which per-cpu list the file is on with a new
    variale in the file struct (packed into a hole on 64-bit archs). Scalability
    could suffer if files are frequently removed from different cpu's list.

    However loads with frequent removal of files imply short interval between
    adding and removing the files, and the scheduler attempts to avoid moving
    processes too far away. Also, even in the case of cross-CPU removal, the
    hardware has much more opportunity to parallelise cacheline transfers with N
    cachelines than with 1.

    A worst-case test of 1 CPU allocating files subsequently being freed by N CPUs
    degenerates to contending on a single lock, which is no worse than before. When
    more than one CPU are allocating files, even if they are always freed by
    different CPUs, there will be more parallelism than the single-lock case.

    Testing results:

    On a 2 socket, 8 core opteron, I measure the number of times the lock is taken
    to remove the file, the number of times it is removed by the same CPU that
    added it, and the number of times it is removed by the same node that added it.

    Booting: locks= 25049 cpu-hits= 23174 (92.5%) node-hits= 23945 (95.6%)
    kbuild -j16 locks=2281913 cpu-hits=2208126 (96.8%) node-hits=2252674 (98.7%)
    dbench 64 locks=4306582 cpu-hits=4287247 (99.6%) node-hits=4299527 (99.8%)

    So a file is removed from the same CPU it was added by over 90% of the time.
    It remains within the same node 95% of the time.

    Tim Chen ran some numbers for a 64 thread Nehalem system performing a compile.

    throughput
    2.6.34-rc2 24.5
    +patch 24.9

    us sys idle IO wait (in %)
    2.6.34-rc2 51.25 28.25 17.25 3.25
    +patch 53.75 18.5 19 8.75

    So significantly less CPU time spent in kernel code, higher idle time and
    slightly higher throughput.

    Single threaded performance difference was within the noise of microbenchmarks.
    That is not to say penalty does not exist, the code is larger and more memory
    accesses required so it will be slightly slower.

    Cc: linux-kernel@vger.kernel.org
    Cc: Tim Chen
    Cc: Andi Kleen
    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • 2dc91abe0   lglock: introduce special lglock and brlock spin locks ... Browse Code »

    lglock: introduce special lglock and brlock spin locks

    This patch introduces "local-global" locks (lglocks). These can be used to:

    - Provide fast exclusive access to per-CPU data, with exclusive access to
    another CPU's data allowed but possibly subject to contention, and to provide
    very slow exclusive access to all per-CPU data.
    - Or to provide very fast and scalable read serialisation, and to provide
    very slow exclusive serialisation of data (not necessarily per-CPU data).

    Brlocks are also implemented as a short-hand notation for the latter use
    case.

    Thanks to Paul for local/global naming convention.

    Cc: linux-kernel@vger.kernel.org
    Cc: Al Viro
    Cc: "Paul E. McKenney"
    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • d996b62a8   tty: fix fu_list abuse ... Browse Code »

    tty: fix fu_list abuse

    tty code abuses fu_list, which causes a bug in remount,ro handling.

    If a tty device node is opened on a filesystem, then the last link to the inode
    removed, the filesystem will be allowed to be remounted readonly. This is
    because fs_may_remount_ro does not find the 0 link tty inode on the file sb
    list (because the tty code incorrectly removed it to use for its own purpose).
    This can result in a filesystem with errors after it is marked "clean".

    Taking idea from Christoph's initial patch, allocate a tty private struct
    at file->private_data and put our required list fields in there, linking
    file and tty. This makes tty nodes behave the same way as other device nodes
    and avoid meddling with the vfs, and avoids this bug.

    The error handling is not trivial in the tty code, so for this bugfix, I take
    the simple approach of using __GFP_NOFAIL and don't worry about memory errors.
    This is not a problem because our allocator doesn't fail small allocs as a rule
    anyway. So proper error handling is left as an exercise for tty hackers.

    [ Arguably filesystem's device inode would ideally be divorced from the
    driver's pseudo inode when it is opened, but in practice it's not clear whether
    that will ever be worth implementing. ]

    Cc: linux-kernel@vger.kernel.org
    Cc: Christoph Hellwig
    Cc: Alan Cox
    Cc: Greg Kroah-Hartman
    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • ee2ffa0df   fs: cleanup files_lock locking ... Browse Code »

    fs: cleanup files_lock locking

    Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
    manipulate the per-sb files list; unexport the files_lock spinlock.

    Cc: linux-kernel@vger.kernel.org
    Cc: Christoph Hellwig
    Cc: Alan Cox
    Acked-by: Andi Kleen
    Acked-by: Greg Kroah-Hartman
    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • b04f784e5   fs: remove extra lookup in __lookup_hash ... Browse Code »

    fs: remove extra lookup in __lookup_hash

    Optimize lookup for create operations, where no dentry should often be
    common-case. In cases where it is not, such as unlink, the added overhead
    is much smaller than the removed.

    Also, move comments about __d_lookup racyness to the __d_lookup call site.
    d_lookup is intuitive; __d_lookup is what needs commenting. So in that same
    vein, add kerneldoc comments to __d_lookup and clean up some of the comments:

    - We are interested in how the RCU lookup works here, particularly with
    renames. Make that explicit, and point to the document where it is explained
    in more detail.
    - RCU is pretty standard now, and macros make implementations pretty mindless.
    If we want to know about RCU barrier details, we look in RCU code.
    - Delete some boring legacy comments because we don't care much about how the
    code used to work, more about the interesting parts of how it works now. So
    comments about lazy LRU may be interesting, but would better be done in the
    LRU or refcount management code.

    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • 2a4419b5b   fs: fs_struct rwlock to spinlock ... Browse Code »

    fs: fs_struct rwlock to spinlock

    struct fs_struct.lock is an rwlock with the read-side used to protect root and
    pwd members while taking references to them. Taking a reference to a path
    typically requires just 2 atomic ops, so the critical section is very small.
    Parallel read-side operations would have cacheline contention on the lock, the
    dentry, and the vfsmount cachelines, so the rwlock is unlikely to ever give a
    real parallelism increase.

    Replace it with a spinlock to avoid one or two atomic operations in typical
    path lookup fastpath.

    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • 44672e4fb   apparmor: use task path helpers ... Browse Code »

    apparmor: use task path helpers

    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • baa038907   fs: dentry allocation consolidation ... Browse Code »

    fs: dentry allocation consolidation

    There are 2 duplicate copies of code in dentry allocation in path lookup.
    Consolidate them into a single function.

    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • 2e2e88ea8   fs: fix do_lookup false negative ... Browse Code »

    fs: fix do_lookup false negative

    In do_lookup, if we initially find no dentry, we take the directory i_mutex and
    re-check the lookup. If we find a dentry there, then we revalidate it if
    needed. However if that revalidate asks for the dentry to be invalidated, we
    return -ENOENT from do_lookup. What should happen instead is an attempt to
    allocate and lookup a new dentry.

    This is probably not noticed because it is rare. It is only reached if a
    concurrent create races in first (in which case, the dentry probably won't be
    invalidated anyway), or if the racy __d_lookup has failed due to a
    false-negative (which is very rare).

    Fix this by removing code and have it use the normal reval path.

    Signed-off-by: Nick Piggin
    Signed-off-by: Al Viro

    Nick Piggin
     
  • 3a48ee8a4   mbcache: Limit the maximum number of cache entries ... Browse Code »

    Limit the maximum number of mb_cache entries depending on the number of
    hash buckets: if the only limit to the number of cache entries is the
    available memory the hash chains can grow very long, taking a long time
    to search.

    At least partially solves https://bugzilla.lustre.org/show_bug.cgi?id=22771.

    Signed-off-by: Andreas Gruenbacher
    Signed-off-by: Al Viro

    Andreas Gruenbacher
     
  • 3b6036d14   hostfs ->follow_link() braino ... Browse Code »

    we want the assignment to err done inside the if () to be
    visible after it, so (re)declaring err inside if () body
    is wrong.

    Signed-off-by: Al Viro

    Al Viro
     
  • 850a496f9   hostfs: dumb (and usually harmless) tpyo - strncpy instead of strlcpy ... Browse Code »

    ... not harmless in this case - we have a string in the end of buffer
    already.

    Signed-off-by: Al Viro

    Al Viro
     
  • 9cb569d60   remove SWRITE* I/O types ... Browse Code »

    These flags aren't real I/O types, but tell ll_rw_block to always
    lock the buffer instead of giving up on a failed trylock.

    Instead add a new write_dirty_buffer helper that implements this semantic
    and use it from the existing SWRITE* callers. Note that the ll_rw_block
    code had a bug where it didn't promote WRITE_SYNC_PLUG properly, which
    this patch fixes.

    In the ufs code clean up the helper that used to call ll_rw_block
    to mirror sync_dirty_buffer, which is the function it implements for
    compound buffers.

    Signed-off-by: Christoph Hellwig
    Signed-off-by: Al Viro

    Christoph Hellwig
     
  • 87e99511e   kill BH_Ordered flag ... Browse Code »

    Instead of abusing a buffer_head flag just add a variant of
    sync_dirty_buffer which allows passing the exact type of write
    flag required.

    Signed-off-by: Christoph Hellwig
    Signed-off-by: Al Viro

    Christoph Hellwig
     
  • dad5eb6da   vfs: update ctime when changing the file's permission by setfacl ... Browse Code »

    generic_acl_set didn't update the ctime of the file when its permission was
    changed.

    Steps to reproduce:
    # touch aaa
    # stat -c %Z aaa
    1275289822
    # setfacl -m 'u::x,g::x,o::x' aaa
    # stat -c %Z aaa
    1275289822 .

    CC: Al Viro
    Signed-off-by: Jan Kara
    Signed-off-by: Al Viro

    Jan Kara
     
  • b845ff8f3   cramfs: only unlock new inodes ... Browse Code »

    Commit 77b8a75f5bb introduced a warning at fs/inode.c:692 unlock_new_inode(),
    caused by unlock_new_inode() being called on existing inodes as well.

    This patch changes setup_inode() to only call unlock_new_inode() for I_NEW
    inodes.

    Signed-off-by: Alexander Shishkin
    Signed-off-by: Al Viro

    Alexander Shishkin
     
  • f4ae2faa4   fix reiserfs_evict_inode end_writeback second call ... Browse Code »

    reiserfs_evict_inode calls end_writeback two times hitting
    kernel BUG at fs/inode.c:298 becase inode->i_state is I_CLEAR already.

    Signed-off-by: Sergey Senozhatsky
    Signed-off-by: Al Viro

    Sergey Senozhatsky
     

16 Aug, 2010

10 commits

  • da5cabf80   Linux 2.6.36-rc1 Browse Code »
    Linus Torvalds
     
  • 2245ba2a3   Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 ... Browse Code »

    * 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
    gcc-4.6: ACPI: fix unused but set variables in ACPI
    ACPI thermal: make procfs I/F depend on CONFIG_ACPI_PROCFS
    ACPI video: make procfs I/F depend on CONFIG_ACPI_PROCFS
    ACPI processor: remove deprecated ACPI procfs I/F
    ACPI power_resource: remove unused procfs I/F
    ACPI: remove deprecated ACPI procfs I/F
    ACPI: introduce drivers/acpi/sysfs.c
    ACPI: introduce module parameter acpi.aml_debug_output
    ACPI: introduce drivers/acpi/debugfs.c
    ACPI, APEI, ERST debug support
    ACPI, APEI, Manage GHES as platform devices
    ACPI, APEI, Rename CPER and GHES severity constants
    ACPI, APEI, Fix a typo of error path of apei_resources_request
    ACPI / ACPICA: Fix reference counting problems with GPE handlers
    ACPI: Add the check of ADR flag in course of finding ACPI handle for PCI device
    ACPI / Sleep: Drop acpi_suspend_finish()
    ACPI / Sleep: Consolidate suspend and hibernation routines
    ACPI / Wakeup: Simplify enabling of wakeup devices
    ACPI / Sleep: Rework enabling wakeup devices
    ACPI / Sleep: Free NVS copy if suspending of devices fails

    Fixed up totally buggered "ACPI: fix unused but set variables in ACPI"
    patch that doesn't even compile in the merge.

    Thanks to Sedat Dilek for noticing the
    breakage before I even pulled. And a big "Grrr.." at Len for not even
    bothering to compile the tree before asking me to pull.

    Linus Torvalds
     
  • e2e96c663   Merge git://git.infradead.org/iommu-2.6 ... Browse Code »

    * git://git.infradead.org/iommu-2.6:
    intel-iommu: Fix 32-bit build warning with __cmpxchg()
    intr-remap: allow disabling source id checking

    Linus Torvalds
     
  • 7355a5a65   Merge git://git.infradead.org/mtd-2.6 ... Browse Code »

    * git://git.infradead.org/mtd-2.6:
    mtd/nand_ids: Fix buswidth
    mtd/m25p80: fix test for end of loop
    mtd/m25p80: retlen is never NULL
    MIPS: Fix gen_nand probe structures contents
    gen_nand: Test if nr_chips field is valid
    BFIN: Fix gen_nand probe structures contents
    nand/denali: move all hardware initialization work to denali_hw_init
    nand/denali: Add a page check in denali_read_page & denali_read_page_raw
    nand/denali: use cpu_relax() while waiting for hardware interrupt
    nand/denali: change read_status function method
    nand/denali: Fixed check patch warnings
    ARM: Fix gen_nand probe structures contents
    mtd/nand_base: fix kernel-doc warnings & typos
    nand/denali: use dev_xx debug function to replace nand_dbg_print and some printk
    nand/denali: Fixed handle ECC error bugs
    nand/denali: use iowrite32() to replace denali_write32()
    nand/denali: Fixed probe function bugs

    Linus Torvalds
     
  • 7a1b29a82   Merge git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile ... Browse Code »

    * git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile:
    arch/tile: don't validate CROSS_COMPILE needlessly
    arch/tile: export only COMMAND_LINE_SIZE to userspace.
    arch/tile: rename ARCH_KMALLOC_MINALIGN to ARCH_DMA_MINALIGN
    arch/tile: Rename the hweight() implementations to __arch_hweight()
    arch/tile: extend syscall ABI to set r1 on return as well.
    arch/tile: Various cleanups.
    arch/tile: support backtracing on TILE-Gx
    arch/tile: Fix a couple of issues with the COMPAT code for TILE-Gx.
    arch/tile: Use separate, better minsec values for clocksource and sched_clock.
    arch/tile: correct a bug in freeing bootmem by VA for the optional second initrd.
    arch: tile: mm: pgtable.c: Removed duplicated #include
    arch: tile: kernel/proc.c Removed duplicated #include
    Add fanotify syscalls to .
    arch/tile: support new kunmap_atomic() naming convention.
    tile: remove unused ISA_DMA_THRESHOLD define

    Conflicts in arch/tile/configs/tile_defconfig (pick the mainline version
    with the reduced defconfig).

    Linus Torvalds
     
  • a5854dd7f   arch/tile: don't validate CROSS_COMPILE needlessly ... Browse Code »

    With this change, the arch/tile Makefile will only check for a valid
    combination of CROSS_COMPILE vs "uname -m" for a few common targets
    that are typically the ones we get wrong (vmlinux, all, and modules).
    The change handles the case of an empty "make" goal like "make all".

    Signed-off-by: Chris Metcalf
    Reviewed-by: Sam Ravnborg

    Chris Metcalf
     
  • d7824370e   mm: fix up some user-visible effects of the stack guard page ... Browse Code »

    This commit makes the stack guard page somewhat less visible to user
    space. It does this by:

    - not showing the guard page in /proc//maps

    It looks like lvm-tools will actually read /proc/self/maps to figure
    out where all its mappings are, and effectively do a specialized
    "mlockall()" in user space. By not showing the guard page as part of
    the mapping (by just adding PAGE_SIZE to the start for grows-up
    pages), lvm-tools ends up not being aware of it.

    - by also teaching the _real_ mlock() functionality not to try to lock
    the guard page.

    That would just expand the mapping down to create a new guard page,
    so there really is no point in trying to lock it in place.

    It would perhaps be nice to show the guard page specially in
    /proc//maps (or at least mark grow-down segments some way), but
    let's not open ourselves up to more breakage by user space from programs
    that depends on the exact deails of the 'maps' file.

    Special thanks to Henrique de Moraes Holschuh for diving into lvm-tools
    source code to see what was going on with the whole new warning.

    Reported-and-tested-by: François Valenduc
    Cc: stable@kernel.org
    Signed-off-by: Linus Torvalds

    Linus Torvalds
     
  • 1b68c9596   Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 ... Browse Code »

    * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6:
    ALSA: sound/usb/format: silence uninitialized variable warnings
    MAINTAINERS: Add Ian Lartey as comaintaner for Wolfson devices
    MAINTAINERS: Make Wolfson entry also cover CODEC drivers
    ASoC: Only tweak WM8994 chip configuration on devices up to rev D
    ASoC: Optimise DSP performance for WM8994
    ALSA: hda - Fix dynamic ADC change working again
    ALSA: hda - Restrict PCM parameters per ELD information over HDMI
    sound: oss: sh_dac_audio.c removed duplicated #include

    Linus Torvalds
     
  • 5a4179460   Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6 ... Browse Code »

    * 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6:
    intel_idle: recognize Lincroft Atom Processor
    intel_idle: no longer EXPERIMENTAL
    intel_idle: disable module support
    intel_idle: add support for Westmere-EX
    intel_idle: delete power_policy modparam, and choose substate functions
    intel_idle: delete substates DEBUG modparam

    Linus Torvalds
     
  • 3b3c1b9d0   arch/tile: export only COMMAND_LINE_SIZE to userspace. ... Browse Code »

    This fixes a failure in "make headers_check" for tile.
    I hadn't realized this file was exported to userspace by default.

    Signed-off-by: Chris Metcalf

    Chris Metcalf
     

15 Aug, 2010

13 commits