[VM PATCH] rotate_reclaimable_page fails frequently

[Shantanu Goel <sgoel01@yahoo.com>]

Hi,

It seems rotate_reclaimable_page fails most of the
time due the page not being on the LRU when kswapd
calls writepage().  The filesystem in my tests is
ext3.  The attached patch against 2.6.16-rc2 moves the
page to the LRU before calling writepage().  Below are
results for a write test with:

dd if=/dev/zero of=test bs=1024k count=1024

To trigger the writeback path with the default dirty
ratios, I set swappiness to 55 and mapped memory to
about 80%.

w/o patch (/proc/sys/vm/wb_put_lru = 0):

pgrotcalls              25852
pgrotnonlru             25834
pgrotated               18

with patch (/proc/sys/vm/wb_put_lru = 1):

pgrotcalls              26616
pgrotated               26616

Thanks,
Shantanu


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Attachment: vmscan-rotate-fix.patch
Description: 1824612824-vmscan-rotate-fix.patch