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

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