linux-kernel - Re: [PATCH 2.6.20-rc5 1/1] MM: enhance Linux swap subsystem

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Date:	Mon, 22 Jan 2007 23:00:41 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	"yunfeng zhang" <zyf.zeroos@...il.com>
Cc:	"Rik van Riel" <riel@...hat.com>, "Pavel Machek" <pavel@....cz>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.20-rc5 1/1] MM: enhance Linux swap subsystem

yunfeng zhang wrote:
> My patch is based on my new idea to Linux swap subsystem, you can find
> more in Documentation/vm_pps.txt which isn't only patch illustration but
> also file changelog. In brief, SwapDaemon should scan and reclaim pages on
> UserSpace::vmalist other than current zone::active/inactive. The change
> will conspicuously enhance swap subsystem performance by
>
> 1) SwapDaemon can collect the statistic of process acessing pages and by
> it unmaps ptes, SMP specially benefits from it for we can use
> flush_tlb_range to unmap ptes batchly rather than frequently TLB IPI
> interrupt per a page in current Linux legacy swap subsystem.
> 2) Page-fault can issue better readahead requests since history data shows
> all related pages have conglomerating affinity. In contrast, Linux
> page-fault readaheads the pages relative to the SwapSpace position of
> current page-fault page.
> 3) It's conformable to POSIX madvise API family.
> 4) It simplifies Linux memory model dramatically. Keep it in mind that new
> swap strategy is from up to down. In fact, Linux legacy swap subsystem is
> maybe the only one from down to up.
>
> Other problems asked about my pps are
> 1) There isn't new lock order in my pps, it's compliant to Linux lock
> order defined in mm/rmap.c.
> 2) When a memory inode is low, you can set scan_control::reclaim_node to
> let my kppsd to reclaim the memory inode page.

Patched against 2.6.19 leads to:

mm/vmscan.c: In function `shrink_pvma_scan_ptes':
mm/vmscan.c:1340: too many arguments to function `page_remove_rmap'

So changed
 page_remove_rmap(series.pages[i], vma);
to
 page_remove_rmap(series.pages[i]);

But your patch doesn't offer any swap-performance improvement for both swsusp 
or tmpfs.  Swap-in is still half speed of Swap-out.


Thanks!

--
Al

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