Re: speeding up swapoff

From: Eric W. Biederman
Date: Thu Aug 30 2007 - 04:27:58 EST


Hugh Dickins <hugh@xxxxxxxxxxx> writes:

> The speedups I've imagined making, were a need demonstrated, have
> been more on the lines of batching (dealing with a range of pages
> in one go) and hashing (using the swapmap's ushort, so often 1 or
> 2 or 3, to hold an indicator of where to look for its references).

There is one other possibility. Typically the swap code is using
compatibility disk I/O functions instead of the best the kernel
can offer. I haven't looked recently but it might be worth just
making certain that there isn't some low-level optimization or
cleanup possible on that path. Although I may just be thinking
of swapfiles.

I know there were tremendous gains ago when I removed the functions
that wrote pages synchronously to swapfiles.

Eric
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