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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