[#3877] echo 0 > /proc/sys/vm/pagecache_ratio may hang shell

Submitted By: Yi Li

Open Date

2008-01-31 21:23:23 Close Date

2008-03-17 18:47:23

Priority:

Very Low Assignee:

Nobody

Status:

Closed Fixed In Release:

N/A

Found In Release:

N/A Release:

svn trunk

Category:

N/A Board:

STAMP

Processor:

BF537 Silicon Revision:

Is this bug repeatable?:

Yes Resolution:

Fixed

Uboot version or rev.:

Toolchain version or rev.:

svn trunk

App binary format:

N/A

Summary: echo 0 > /proc/sys/vm/pagecache_ratio may hang shell

Details:

Just log here - not sure this is expected behavior or bug.

When using jffs2 in NOR flash as rootfs, doing bellow operation will hang the shell.

root:/> mount

rootfs on / type rootfs (rw)

/dev/root on / type jffs2 (rw)

proc on /proc type proc (rw)

ramfs on /var type ramfs (rw)

sysfs on /sys type sysfs (rw)

root:/> echo 50 > /proc/sys/vm/pagecache_ratio

root:/> echo 3 > /proc/sys/vm/drop_caches

root:/> cat /proc/meminfo

MemTotal: 55324 kB

MemFree: 51248 kB

Buffers: 0 kB

Cached: 148 kB

SwapCached: 0 kB

Active: 36 kB

Inactive: 112 kB

SwapTotal: 0 kB

SwapFree: 0 kB

Dirty: 0 kB

Writeback: 0 kB

AnonPages: 0 kB

Mapped: 0 kB

Slab: 1180 kB

SReclaimable: 160 kB

SUnreclaim: 1020 kB

PageTables: 0 kB

NFS_Unstable: 0 kB

Bounce: 0 kB

CommitLimit: 27660 kB

Committed_AS: 0 kB

VmallocTotal: 0 kB

VmallocUsed: 0 kB

VmallocChunk: 0 kB

root:/> echo 0 > /proc/sys/vm/pagecache_ratio

root:/> echo 3 > /proc/sys/vm/drop_caches

root:/> cat /proc/meminfo

[shell hangs here, it is responsive, but this command never returns]

("echo 1 > /proc/sys/vm/pagecache_ratio" works well)

Follow-ups

--- Sonic Zhang 2008-02-01 01:01:05

The min value should be 10%. How about limit the acceptable value in the driver?

--- Yi Li 2008-02-01 04:07:08

where can I find the 10% limit? I am thinking 0% would disable page cache at

all.

--- Sonic Zhang 2008-02-01 04:15:33

Linux is based on page cache. It can not be disabled completely.

--- Sonic Zhang 2008-02-29 01:20:16

Fixed. Now 10 is the min value.

--- Mike Frysinger 2008-03-17 18:47:23

pagecache no longer in the kernel

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