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Re: [Qemu-devel] [PATCH] main-loop: drop spin_counter
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] main-loop: drop spin_counter |
Date: |
Thu, 31 May 2018 14:34:32 +0100 |
User-agent: |
Mutt/1.9.5 (2018-04-13) |
On Wed, May 30, 2018 at 08:42:38PM +0100, Stefan Hajnoczi wrote:
> Commit d759c951f3287fad04210a52f2dc93f94cf58c7f ("replay: push
> replay_mutex_lock up the call tree") removed the !timeout lock
> optimization in the main loop.
>
> The idea of the optimization was to avoid ping-pongs between threads by
> keeping the Big QEMU Lock held across non-blocking (!timeout) main loop
> iterations.
>
> A warning is printed when the main loop spins without releasing BQL for
> long periods of time. These warnings were supposed to aid debugging but
> in practice they just alarm users. They are considered noise because
> the cause of spinning is not shown and is hard to find.
>
> Now that the lock optimization has been removed, there is no danger of
> hogging the BQL. Drop the spin counter and the infamous warning.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> util/main-loop.c | 25 -------------------------
> tests/qemu-iotests/common.filter | 1 -
> 2 files changed, 26 deletions(-)
Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block
Stefan
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