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Re: [Qemu-devel] [PATCH v6 70/73] cpu: protect CPU state with cpu->lock

From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH v6 70/73] cpu: protect CPU state with cpu->lock instead of the BQL
Date: Wed, 20 Feb 2019 09:25:00 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 1/29/19 4:48 PM, Emilio G. Cota wrote:
> Use the per-CPU locks to protect the CPUs' state, instead of
> using the BQL. These locks are uncontended (they are mostly
> acquired by the corresponding vCPU thread), so acquiring them
> is cheaper than acquiring the BQL, which particularly in
> MTTCG can be contended at high core counts.
> In this conversion we drop qemu_cpu_cond and qemu_pause_cond,
> and use cpu->cond instead.
> In qom/cpu.c we can finally remove the ugliness that
> results from having to hold both the BQL and the CPU lock;
> now we just have to grab the CPU lock.
> Signed-off-by: Emilio G. Cota <address@hidden>
> ---
>  include/qom/cpu.h |  20 ++--
>  cpus.c            | 280 ++++++++++++++++++++++++++++++++++------------
>  qom/cpu.c         |  29 +----
>  3 files changed, 225 insertions(+), 104 deletions(-)

Reviewed-by: Richard Henderson <address@hidden>


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