linux-kernel - [RFC] kswapd: Kernel Swapper performance

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Message-Id: <200610282031.17451.a1426z@gawab.com>
Date:	Sat, 28 Oct 2006 20:31:17 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	linux-kernel@...r.kernel.org
Subject: [RFC] kswapd: Kernel Swapper performance

One thing that has improved in 2.6, wrt 2.4, is swapper performance.  And the 
difference isn't small either: ~5 fold increase in swapin performance.

But swapin performance still lags swapout performance by 50%, which is a bit 
odd, considering swapin to be a read from disk, usually faster, and swapout 
to be a write to disk, usually slower.

Now, this slowdown could be explained by additional seek action, caused by 
different apps paging-in at different times with different locations on 
swap.

Yet, even a single app paging-out consecutive pages, and paging-in the same 
pages in one go, exhibits this upside-down swapout/swapin performance ratio.

Improving this ratio could possibly yield a dramatic improvement in system 
performance under memory load (think tmpfs/swsusp/...).

Thanks!

--
Al

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