Re: [PATCH] 2.5: push BKL out of llseek

From: Robert Love (rml@tech9.net)
Date: Tue Jan 29 2002 - 21:20:10 EST


On Tue, 2002-01-29 at 20:26, Andrew Morton wrote:

> Just a little word of caution here. Remember the
> apache-flock-synchronisation fiasco, where removal
> of the BKL halved Apache throughput on 8-way x86.
>
> This was because the BKL removal turned serialisation
> on a quick codepath from a spinlock into a schedule().

I feared this too, but eventually I decided it was worth it and
benchmarks backed that up. If nothing else this is yet-another-excuse
for locks that can spin-then-sleep.

I posted dbench results, which show a positive gain even on 2-way for
multiple client loads.

        Robert Love

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