Re: [v5][PATCH 6/6] mm: vmscan: drain batch list during long operations

[Minchan Kim <minchan@kernel.org>]

On Mon, Jun 03, 2013 at 01:02:10PM -0700, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> This was a suggestion from Mel:
> 
> 	http://lkml.kernel.org/r/20120914085634.GM11157@csn.ul.ie
> 
> Any pages we collect on 'batch_for_mapping_removal' will have
> their lock_page() held during the duration of their stay on the
> list.  If some other user is trying to get at them during this
> time, they might end up having to wait.
> 
> This ensures that we drain the batch if we are about to perform a
> pageout() or congestion_wait(), either of which will take some
> time.  We expect this to help mitigate the worst of the latency
> increase that the batching could cause.
> 
> I added some statistics to the __remove_mapping_batch() code to
> track how large the lists are that we pass in to it.  With this
> patch, the average list length drops about 10% (from about 4.1 to
> 3.8).  The workload here was a make -j4 kernel compile on a VM
> with 200MB of RAM.
> 
> I've still got the statistics patch around if anyone is
> interested.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>


-- 
Kind regards,
Minchan Kim

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