Re: [PATCH 1/3] vm: kswapd incmin

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• In reply to: Nick Piggin: "Re: [PATCH 1/3] vm: kswapd incmin"
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Date:	Mon, 7 Nov 2005 16:43:06 -0200
To: Nick Piggin <nickpiggin@yahoo.com.au>

On Tue, Nov 08, 2005 at 10:08:53AM +1100, Nick Piggin wrote:
> Marcelo Tosatti wrote:
> >Hi Nick,
> >
> >Looks nice, much easier to read than before.
> >
>
> Hi Marcelo,
>
> Thanks! That was one of the main aims.
>
> >One comment: you change the pagecache/slab scanning ratio by moving
> >shrink_slab() outside of the zone loop.
> >
> >This means that for each kswapd iteration will scan "lru_pages"
> >SLAB entries, instead of "lru_pages*NR_ZONES" entries.
> >
> >Can you comment on that?
> >
>
> I believe I have tried to get it right, let me explain. lru_pages
> is just used as the divisor for the ratio between lru scanning
> and slab scanning. So long as it is kept constant across calls to
> shrink_slab, there should be no change in behaviour.
>
> The the nr_scanned variable is the other half of the equation that
> controls slab shrinking. I have changed from:
>
> lru_pages = total_node_lru_pages;
> for each zone in node {
> shrink_zone();
> shrink_slab(zone_scanned, lru_pages);
> }
>
> To:
>
> lru_pages = 0;
> for each zone in node {
> shrink_zone();
> lru_pages += zone_lru_pages;
> }
> shrink_slab(total_zone_scanned, lru_pages);
>
> So the ratio remains basically the same
> [eg. 10/100 + 20/100 + 30/100 = (10+20+30)/100]
>
> 2 reasons for doing this. The first is just efficiency and better
> rounding of the divisions.
>
> The second is that within the for_each_zone loop, we are able to
> set all_unreclaimable without worrying about slab, because the
> final shrink_slab at the end will clear all_unreclaimable if any
> zones have had slab pages freed up.
>
> I believe it generally should result in more consistent reclaim
> across zones, and also matches direct reclaim better.
>
> Hope this made sense,

Yes, makes sense. My reading was not correct.

Sounds great.
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• Previous message: Andrew Morton: "Re: [dm-devel] Re: [PATCH resubmit] do_mount: reduce stack consumption"
• In reply to: Nick Piggin: "Re: [PATCH 1/3] vm: kswapd incmin"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]