Re: [VM PATCH] rotate_reclaimable_page fails frequently

["Mika Penttilä" <mika.penttila@kolumbus.fi>]

Shantanu Goel wrote:

>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
>
>
>__________________________________________________
>  
>
 I think this BUGs easily because shrink_cache doesn't expect to see 
unfreeable pages put back to LRU.

--Mika