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90afa5de6f
A bug was brought to my attention against a distro kernel but it affects
mainline and I believe problems like this have been reported in various
guises on the mailing lists although I don't have specific examples at the
moment.
The reported problem was that malloc() stalled for a long time (minutes in
some cases) if a large tmpfs mount was occupying a large percentage of
memory overall. The pages did not get cleaned or reclaimed by
zone_reclaim() because the zone_reclaim_mode was unsuitable, but the lists
are uselessly scanned frequencly making the CPU spin at near 100%.
This patchset intends to address that bug and bring the behaviour of
zone_reclaim() more in line with expectations which were noticed during
investigation. It is based on top of mmotm and takes advantage of
Kosaki's work with respect to zone_reclaim().
Patch 1 fixes the heuristics that zone_reclaim() uses to determine if the
scan should go ahead. The broken heuristic is what was causing the
malloc() stall as it uselessly scanned the LRU constantly. Currently,
zone_reclaim is assuming zone_reclaim_mode is 1 and historically it
could not deal with tmpfs pages at all. This fixes up the heuristic so
that an unnecessary scan is more likely to be correctly avoided.
Patch 2 notes that zone_reclaim() returning a failure automatically means
the zone is marked full. This is not always true. It could have
failed because the GFP mask or zone_reclaim_mode were unsuitable.
Patch 3 introduces a counter zreclaim_failed that will increment each
time the zone_reclaim scan-avoidance heuristics fail. If that
counter is rapidly increasing, then zone_reclaim_mode should be
set to 0 as a temporarily resolution and a bug reported because
the scan-avoidance heuristic is still broken.
This patch:
On NUMA machines, the administrator can configure zone_reclaim_mode that
is a more targetted form of direct reclaim. On machines with large NUMA
distances for example, a zone_reclaim_mode defaults to 1 meaning that
clean unmapped pages will be reclaimed if the zone watermarks are not
being met.
There is a heuristic that determines if the scan is worthwhile but the
problem is that the heuristic is not being properly applied and is
basically assuming zone_reclaim_mode is 1 if it is enabled. The lack of
proper detection can manfiest as high CPU usage as the LRU list is scanned
uselessly.
Historically, once enabled it was depending on NR_FILE_PAGES which may
include swapcache pages that the reclaim_mode cannot deal with. Patch
vmscan-change-the-number-of-the-unmapped-files-in-zone-reclaim.patch by
Kosaki Motohiro noted that zone_page_state(zone, NR_FILE_PAGES) included
pages that were not file-backed such as swapcache and made a calculation
based on the inactive, active and mapped files. This is far superior when
zone_reclaim==1 but if RECLAIM_SWAP is set, then NR_FILE_PAGES is a
reasonable starting figure.
This patch alters how zone_reclaim() works out how many pages it might be
able to reclaim given the current reclaim_mode. If RECLAIM_SWAP is set in
the reclaim_mode it will either consider NR_FILE_PAGES as potential
candidates or else use NR_{IN}ACTIVE}_PAGES-NR_FILE_MAPPED to discount
swapcache and other non-file-backed pages. If RECLAIM_WRITE is not set,
then NR_FILE_DIRTY number of pages are not candidates. If RECLAIM_SWAP is
not set, then NR_FILE_MAPPED are not.
[kosaki.motohiro@jp.fujitsu.com: Estimate unmapped pages minus tmpfs pages]
[fengguang.wu@intel.com: Fix underflow problem in Kosaki's estimate]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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| .. | ||
| ABI | ||
| accounting | ||
| acpi | ||
| aoe | ||
| arm | ||
| auxdisplay | ||
| blackfin | ||
| block | ||
| blockdev | ||
| cdrom | ||
| cgroups | ||
| connector | ||
| console | ||
| cpu-freq | ||
| cpuidle | ||
| cris | ||
| crypto | ||
| development-process | ||
| device-mapper | ||
| DocBook | ||
| driver-model | ||
| dvb | ||
| early-userspace | ||
| fault-injection | ||
| fb | ||
| filesystems | ||
| firmware_class | ||
| frv | ||
| hwmon | ||
| i2c | ||
| i2o | ||
| ia64 | ||
| ide | ||
| infiniband | ||
| input | ||
| ioctl | ||
| isdn | ||
| ja_JP | ||
| kbuild | ||
| kdump | ||
| ko_KR | ||
| laptops | ||
| lguest | ||
| m68k | ||
| make | ||
| mips | ||
| misc-devices | ||
| mn10300 | ||
| mtd | ||
| namespaces | ||
| netlabel | ||
| networking | ||
| parisc | ||
| PCI | ||
| pcmcia | ||
| power | ||
| powerpc | ||
| prctl | ||
| RCU | ||
| s390 | ||
| scheduler | ||
| scsi | ||
| serial | ||
| sh | ||
| sound | ||
| sparc | ||
| spi | ||
| sysctl | ||
| telephony | ||
| thermal | ||
| timers | ||
| trace | ||
| uml | ||
| usb | ||
| video4linux | ||
| vm | ||
| w1 | ||
| watchdog | ||
| wimax | ||
| x86 | ||
| zh_CN | ||
| 00-INDEX | ||
| applying-patches.txt | ||
| atomic_ops.txt | ||
| bad_memory.txt | ||
| basic_profiling.txt | ||
| binfmt_misc.txt | ||
| braille-console.txt | ||
| bt8xxgpio.txt | ||
| BUG-HUNTING | ||
| c2port.txt | ||
| cachetlb.txt | ||
| Changes | ||
| CodingStyle | ||
| cpu-hotplug.txt | ||
| cpu-load.txt | ||
| cputopology.txt | ||
| credentials.txt | ||
| dcdbas.txt | ||
| debugging-modules.txt | ||
| debugging-via-ohci1394.txt | ||
| dell_rbu.txt | ||
| devices.txt | ||
| DMA-API.txt | ||
| DMA-attributes.txt | ||
| DMA-ISA-LPC.txt | ||
| DMA-mapping.txt | ||
| dmaengine.txt | ||
| dontdiff | ||
| dynamic-debug-howto.txt | ||
| edac.txt | ||
| eisa.txt | ||
| email-clients.txt | ||
| exception.txt | ||
| feature-removal-schedule.txt | ||
| futex-requeue-pi.txt | ||
| gpio.txt | ||
| highuid.txt | ||
| HOWTO | ||
| hw_random.txt | ||
| ics932s401 | ||
| initrd.txt | ||
| Intel-IOMMU.txt | ||
| io-mapping.txt | ||
| IO-mapping.txt | ||
| io_ordering.txt | ||
| iostats.txt | ||
| IPMI.txt | ||
| IRQ-affinity.txt | ||
| IRQ.txt | ||
| irqflags-tracing.txt | ||
| isapnp.txt | ||
| java.txt | ||
| kernel-doc-nano-HOWTO.txt | ||
| kernel-docs.txt | ||
| kernel-parameters.txt | ||
| keys-request-key.txt | ||
| keys.txt | ||
| kmemleak.txt | ||
| kobject.txt | ||
| kprobes.txt | ||
| kref.txt | ||
| ldm.txt | ||
| leds-class.txt | ||
| local_ops.txt | ||
| lockdep-design.txt | ||
| lockstat.txt | ||
| logo.gif | ||
| logo.txt | ||
| magic-number.txt | ||
| Makefile | ||
| ManagementStyle | ||
| markers.txt | ||
| mca.txt | ||
| md.txt | ||
| memory-barriers.txt | ||
| memory-hotplug.txt | ||
| memory.txt | ||
| mono.txt | ||
| mutex-design.txt | ||
| nmi_watchdog.txt | ||
| nommu-mmap.txt | ||
| numastat.txt | ||
| oops-tracing.txt | ||
| parport-lowlevel.txt | ||
| parport.txt | ||
| pi-futex.txt | ||
| pnp.txt | ||
| preempt-locking.txt | ||
| printk-formats.txt | ||
| prio_tree.txt | ||
| rbtree.txt | ||
| rfkill.txt | ||
| robust-futex-ABI.txt | ||
| robust-futexes.txt | ||
| rt-mutex-design.txt | ||
| rt-mutex.txt | ||
| rtc.txt | ||
| SAK.txt | ||
| SecurityBugs | ||
| SELinux.txt | ||
| serial-console.txt | ||
| sgi-ioc4.txt | ||
| sgi-visws.txt | ||
| slow-work.txt | ||
| SM501.txt | ||
| Smack.txt | ||
| sparse.txt | ||
| spinlocks.txt | ||
| stable_api_nonsense.txt | ||
| stable_kernel_rules.txt | ||
| SubmitChecklist | ||
| SubmittingDrivers | ||
| SubmittingPatches | ||
| svga.txt | ||
| sysfs-rules.txt | ||
| sysrq.txt | ||
| tomoyo.txt | ||
| unaligned-memory-access.txt | ||
| unicode.txt | ||
| unshare.txt | ||
| VGA-softcursor.txt | ||
| video-output.txt | ||
| volatile-considered-harmful.txt | ||
| voyager.txt | ||
| zorro.txt | ||
