The patch titled
VM: don't run touch_buffer() during buffercache lookups
has been removed from the -mm tree. Its filename was
vm-dont-run-touch_buffer-during-buffercache-lookups.patch
This patch was dropped because it was withdrawn
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: VM: don't run touch_buffer() during buffercache lookups
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
When userspace reads a directory or a number of inodes it is very common for
the filesystem to be asked to access the same metadata block multiple times in
quick succession. Each lookup will run touch_buffer().
As a consequence of this, large amounts of blockdev pagecache end up nailed on
the VM's active list, marked as referenced. These pages will cause other
active pages to be evicted: mapped executables, swapout, etc.
This is probably wrong. The core problem here is that the kernel is treating
that sudden burst of accesses to the dirents and inodes as multiple touches.
Really we should be treating them as a single touch.
So as an experiment, just remove that touch_buffer() call.
We don't have any tests to determine the effects of this, and nobody will
bother setting one up, so ho hum, this remains in -mm for ever.
This change is probably a bit too aggressive - as a followup, filesystems
should be taught to run touch_buffer() or mark_page_accessed() against this
pagecache on each "independent" access.
The problem is, how to determine when they are "independent"? Perhaps "the
access was to the first inode in the block" and "the access was to the first
directory entry in the block" would suffice. The fs could then implement
use-once via:
if (first inode in block) {
page = find_get_page(...);
if (page)
mark_page_accessed(page);
put_page(page);
}
I don't think there's any point in doing this until we have some decent
testcases.
AFACIT ext2 has never run mark_page_accessed() against its directory
pagecache, so there is no practical way in which ext2 directories _ever_ find
their way onto the inactive list. Nobody appears to have noticed this.
touch_buffer() is unused after this patch, but let's retain it for the above
reasons. I guess we'll need a new probe_buffer() thing to be able to
implement the above use-once algorithm for bh-based metadata.
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/buffer.c | 2 --
1 file changed, 2 deletions(-)
diff -puN fs/buffer.c~vm-dont-run-touch_buffer-during-buffercache-lookups fs/buffer.c
--- a/fs/buffer.c~vm-dont-run-touch_buffer-during-buffercache-lookups
+++ a/fs/buffer.c
@@ -1381,8 +1381,6 @@ __find_get_block(struct block_device *bd
if (bh)
bh_lru_install(bh);
}
- if (bh)
- touch_buffer(bh);
return bh;
}
EXPORT_SYMBOL(__find_get_block);
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
mm-remove-the-might_sleep-from-lock_page.patch
git-tip.patch
markers-make-marker_synchronize_unregister-a-macro.patch
git-powerpc.patch
git-sparc.patch
git-xtensa.patch
git-pci.patch
git-hid.patch
git-v4l-dvb.patch
git-v4l-dvb-git-rejects.patch
git-nfs.patch
git-nfsd.patch
git-dlm.patch
git-scsi.patch
git-tests-fixup.patch
git-ext4.patch
git-ext4-vs-git-ocfs2.patch
git-async_tx.patch
git-net.patch
git-net-conflicts.patch
git-mtd.patch
git-vfs-vs-git-ext4.patch
git-sound.patch
git-sound-vs-git-arm.patch
git-input.patch
git-block.patch
git-block-reject-fix.patch
git-pcmcia-git-rejects.patch
git-battery.patch
git-battery-rejects.patch
git-slab-versus-git-tip.patch
git-mfd.patch
git-drm.patch
revert-usb-usb-remove-info-macro-from-usbh.patch
revert-usb-usb-remove-warn-macro-from-usbh.patch
fix-ttydev-tty-usbserial-kref.patch
drivers-mfd-ucb1400_corec-needs-gpio.patch
drivers-mfd-ucb1400_corec-further-unbork.patch
arch-x86-kernel-early_printkc-remove-unused-enable_debug_console.patch
tick-schedc-suppress-needless-timer-reprogramming.patch
drivers-input-touchscreen-ucb1400_tsc-needs-gpio.patch
led-driver-for-leds-on-pcengines-alix2-and-alix3-boards.patch
libata-blackfin-pata-driver-add-proper-pm-operation-into-atapi-driver.patch
misdn-misc-timerdev-fixes-fix.patch
drivers-net-sfc-falconc-fix-min-warnings.patch
backlight-driver-for-tabletkiosk-sahara-touchit-213-tablet-pc.patch
drivers-scsi-sdh-use-inlined-c-functions-not-macros.patch
scsi-dpt_i2o-is-bust-on-ia64.patch
mm-page_allocc-free_area_init_nodes-fix-inappropriate-use-of-enum.patch
mm-cleanup-to-make-remove_memory-arch-neutral-fix.patch
mm-cleanup-to-make-remove_memory-arch-neutral-fix-fix.patch
vm-dont-run-touch_buffer-during-buffercache-lookups.patch
vmscan-move-isolate_lru_page-to-vmscanc.patch
define-page_file_cache-function.patch
vmscan-split-lru-lists-into-anon-file-sets.patch
unevictable-lru-infrastructure.patch
unevictable-lru-page-statistics.patch
mlock-mlocked-pages-are-unevictable.patch
mlock-mlocked-pages-are-unevictable-fix.patch
mmap-handle-mlocked-pages-during-map-remap-unmap.patch
mmap-handle-mlocked-pages-during-map-remap-unmap-mlock-resubmit-locked_vm-adjustment-as-separate-patch-fix.patch
vmscan-unevictable-lru-scan-sysctl.patch
mlock-make-mlock-error-return-posixly-correct-fix.patch
mm-vmallocc-revert-git-tip-change.patch
mm-rewrite-vmap-layer-fix.patch
mm-rewrite-vmap-layer-fix-fix.patch
mm-rewrite-vmap-layer-fix-fix-fix.patch
revert-mm-vmallocc-revert-git-tip-change.patch
memory_probe-fix-wrong-sysfs-file-attribute-fix.patch
mm-use-a-radix-tree-to-make-do_move_pages-complexity-linear-checkpatch-fixes.patch
h8300-generic_bug-support-checkpatch-fixes.patch
pm-rework-disabling-of-user-mode-helpers-during-suspend-hibernation-cleanup.patch
container-freezer-add-tif_freeze-flag-to-all-architectures-fix.patch
container-freezer-implement-freezer-cgroup-subsystem-checkpatch-fixes.patch
container-freezer-implement-freezer-cgroup-subsystem-uninline-thaw_process-fix.patch
eeepc-laptop-use-standard-interfaces-fix-fix.patch
separate-atomic_t-declaration-from-asm-atomich-into-asm-atomic_defh.patch
make-taint-bit-reliable-v3-fix.patch
kernel-sysc-improve-code-generation.patch
compat-generic-compat-get-settimeofday-checkpatch-fixes.patch
hwmon-pc87360-separate-alarm-files-add-in-min-max-alarms-cleanup.patch
hwmon-pc87360-separate-alarm-files-add-temp-min-max-crit-fault-alarms-cleanup.patch
hwmon-pc87360-separate-alarm-files-add-therm-min-max-crit-alarms-cleanup.patch
drivers-hwmon-applesmcc-remove-unneeded-casts.patch
allow-recursion-in-binfmt_script-and-binfmt_misc-fix.patch
serial-make-uart_ports-ioport-unsigned-long-fix.patch
autofs4-track-uid-and-gid-of-last-mount-requester-fix.patch
autofs4-add-miscellaneous-device-for-ioctls-fix.patch
autofs4-add-miscellaneous-device-for-ioctls-fix-2.patch
rtc-add-device-driver-for-dallas-ds3234-spi-rtc-chip-fix.patch
fb-push-down-the-bkl-in-the-ioctl-handler-checkpatch-fixes.patch
viafb-viafbmodes-viafbtxt-fix-fix.patch
viafb-accelc-accelh-checkpatch-fixes.patch
viafb-dvic-dvih-globalc-and-globalh-checkpatch-fixes.patch
viafb-hwc-hwh-checkpatch-fixes.patch
viafb-viafbdevc-viafbdevh-checkpatch-fixes.patch
fbdev-kconfig-update-fix.patch
fbdev-allow-more-chip-revisions-in-epson-s1d13-video-driver-cleanups.patch
ext2-avoid-printk-floods-in-the-face-of-directory-corruption-checkpatch-fixes.patch
ext3-fix-ext3_dx_readdir-hash-collision-handling-checkpatch-fixes.patch
cgroups-fix-probable-race-with-put_css_set-and-find_css_set-fix.patch
memrlimit-add-memrlimit-controller-accounting-and-control-mm_owner-fix-checkpatch-fixes.patch
message-queues-increase-range-limits-checkpatch-fixes.patch
applicomc-fix-apparently-broken-code-in-do_ac_read.patch
drivers-char-tpm-tpmc-fix-error-patch-memory-leak.patch
tpm-addition-of-pnp_remove-checkpatch-fixes.patch
w1-be-able-to-manually-add-and-remove-slaves-fix.patch
w1-new-driver-ds2431-chip-fix.patch
gru-driver-minor-updates-fix.patch
drivers-rtc-rtc-bq4802c-dont-use-bin_2_bcd-and-bcd_2_bin.patch
x86-sysfs-kill-owner-field-from-attribute-fix.patch
x86-sysfs-kill-owner-field-from-attribute-fix-3.patch
nilfs2-inode-operations-fix.patch
nilfs2-pathname-operations-fix.patch
reiser4.patch
reiser4-tree_lock-fixes.patch
reiser4-tree_lock-fixes-fix.patch
reiser4-semaphore-fix.patch
slb-drop-kmem-cache-argument-from-constructor-reiser4.patch
reiser4-suid.patch
reiser4-track-upstream-changes.patch
page-owner-tracking-leak-detector.patch
nr_blockdev_pages-in_interrupt-warning.patch
slab-leaks3-default-y.patch
put_bh-debug.patch
shrink_slab-handle-bad-shrinkers.patch
getblk-handle-2tb-devices.patch
getblk-handle-2tb-devices-fix.patch
undeprecate-pci_find_device.patch
notify_change-callers-must-hold-i_mutex.patch
profile-likely-unlikely-macros.patch
drivers-net-bonding-bond_sysfsc-suppress-uninitialized-var-warning.patch
w1-build-fix.patch
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