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SubjectRe: [PATCH] Provide an interface to limit total page cache.
The possible cause is a bug in kswapd thread, or shrink_all_memory
cannot be called in kswapd thread.

On 1/15/07, Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote:
>
> Roy Huang wrote:
> > A patch provide a interface to limit total page cache in
> > /proc/sys/vm/pagecache_ratio. The default value is 90 percent. Any
> > feedback is appreciated.
>
> [snip]
>
> I tried to run your patch on PPC64 SMP machine, unfortunately kswapd
> crashes the kernel when the pagecache limit is exceeded!
>
> ->dd if=/dev/zero of=/tmp/foo bs=1M count=1200
> cpu 0x0: Vector: 300 (Data Access) at [c0000000012d7ad0]
> pc: c0000000000976ac: .kswapd+0x3a4/0x4f0
> lr: c0000000000976ac: .kswapd+0x3a4/0x4f0
> sp: c0000000012d7d50
> msr: 8000000000009032
> dar: 0
> dsisr: 42000000
> current = 0xc00000000fed7040
> paca = 0xc00000000063fb80
> pid = 134, comm = kswapd0
> ------------[ cut here ]------------
> enter ? for help
> [c0000000012d7ee0] c000000000069150 .kthread+0x124/0x174
> [c0000000012d7f90] c0000000000247b4 .kernel_thread+0x4c/0x68
> 0:mon>
>
> Steps to recreate fail:
>
> # sync
> # echo 1 > /proc/sys/vm/drop_caches
> MemTotal: 1014584 kB
> MemFree: 905536 kB
> Buffers: 3232 kB
> Cached: 57628 kB
> SwapCached: 0 kB
> Active: 47664 kB
> Inactive: 33160 kB
> SwapTotal: 1526164 kB
> SwapFree: 1526164 kB
> Dirty: 108 kB
> Writeback: 0 kB
> AnonPages: 19976 kB
> Mapped: 15084 kB
> Slab: 19724 kB
> SReclaimable: 8536 kB
> SUnreclaim: 11188 kB
> PageTables: 972 kB
> NFS_Unstable: 0 kB
> Bounce: 0 kB
> CommitLimit: 2033456 kB
> Committed_AS: 87884 kB
> VmallocTotal: 8589934592 kB
> VmallocUsed: 2440 kB
> VmallocChunk: 8589932152 kB
> HugePages_Total: 0
> HugePages_Free: 0
> HugePages_Rsvd: 0
> Hugepagesize: 16384 kB
>
> # echo 50 > /proc/sys/vm/pagecache_ratio
> # dd if=/dev/zero of=/tmp/foo bs=1M count=1200
>
> Basically fill pagecache with overlimit dirty file pages and check
> if the reclaim happened and the limit was not exceeded.
>
> --Vaidy
>
>
>
>
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