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Re: spinlock requests (was RE: [Xen-devel] [Patch] don't spin with irq d

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: spinlock requests (was RE: [Xen-devel] [Patch] don't spin with irq disabled)
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Tue, 31 Mar 2009 14:16:11 -0700
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Keir Fraser wrote:
I suspect the existing uses of rwlock in Xen actually are because that
seemed a natural fit for the code -- obvious split between reader and writer
critical sections -- rather than because of excessive serialisation if using
a normal spinlock. I strongly disbelieve that lock acquire/release is a
significant performance bottleneck for us right now.

Aren't rwlocks sufficiently less efficient than spinlocks that you'd tend to use the latter if you don't think contention is an issue?


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