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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Tue, 22 Mar 2016 09:29:42 +0100
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Subject: Re: [Qemu-devel] [RFC v1 01/11] tcg: move tb_find_fast outside the
 tb_lock critical section
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To: "Emilio G. Cota" <cota@braap.org>, Peter Maydell <peter.maydell@linaro.org>
Cc: mttcg@listserver.greensocs.com, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Mark Burton <mark.burton@greensocs.com>, QEMU Developers <qemu-devel@nongnu.org>, Alvise Rigo <a.rigo@virtualopensystems.com>, Sergey Fedorov <serge.fdrv@gmail.com>, Richard Henderson <rth@twiddle.net>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>, =?UTF-8?B?S09OUkFEIEZyw6lkw6lyaWM=?= <fred.konrad@greensocs.com>



On 22/03/2016 00:59, Emilio G. Cota wrote:
> Good point. Most of my tests have been on x86-on-x86, and the
> difference there (for many CPU-intensive benchmarks such as SPEC) was
> negligible.
> 
> Just tested the current master booting Alex' debian ARM image, without
> LRU, and I see a 20% increase in boot time.
> 
> I'll add per-bucket locks to keep the same behaviour without hurting
> scalability.

You probably should skip the MRU move if the TB is not within the first
N items of the list (e.g. N=4).  Then you take the lock much less.

Paolo