Re: [PATCH 6/6] mm: kswapd: Use the classzone idx that kswapd wasusing for sleeping_prematurely()

[Minchan Kim]

On Thu, Dec 9, 2010 at 8:18 PM, Mel Gorman <mel@xxxxxxxxx> wrote:
> When kswapd is woken up for a high-order allocation, it takes account of
> the highest usable zone by the caller (the classzone idx). During
> allocation, this index is used to select the lowmem_reserve[] that
> should be applied to the watermark calculation in zone_watermark_ok().
>
> When balancing a node, kswapd considers the highest unbalanced zone to be the
> classzone index. This will always be at least be the callers classzone_idx
> and can be higher. However, sleeping_prematurely() always considers the
> lowest zone (e.g. ZONE_DMA) to be the classzone index. This means that
> sleeping_prematurely() can consider a zone to be balanced that is unusable
> by the allocation request that originally woke kswapd. This patch changes
> sleeping_prematurely() to use a classzone_idx matching the value it used
> in balance_pgdat().
>
> Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>

Nice catch! and it does make sense to me.

-- 
Kind regards,
Minchan Kim
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