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([2001:8003:1d71:4f01:4dac:f487:9ea0:53e8]) by smtp.gmail.com with ESMTPSA id lr8sm3982366pjb.11.2022.01.26.13.40.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Jan 2022 13:40:49 -0800 (PST) Subject: Re: [PATCH 1/2] softmmu/cpus: Check if the cpu work list is empty atomically To: Idan Horowitz , qemu-devel@nongnu.org References: <20220114004358.299534-1-idan.horowitz@gmail.com> From: Richard Henderson Message-ID: <2c467b27-2471-2f54-b9ce-3282190378e9@linaro.org> Date: Thu, 27 Jan 2022 08:40:44 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20220114004358.299534-1-idan.horowitz@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2607:f8b0:4864:20::102d (failed) Received-SPF: pass client-ip=2607:f8b0:4864:20::102d; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x102d.google.com X-Spam_score_int: -12 X-Spam_score: -1.3 X-Spam_bar: - X-Spam_report: (-1.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/14/22 11:43 AM, Idan Horowitz wrote: > Instead of taking the lock of the cpu work list in order to check if it's > empty, we can just read the head pointer atomically. This decreases > cpu_work_list_empty's share from 5% to 1.3% in a profile of icount-enabled > aarch64-softmmu. > > Signed-off-by: Idan Horowitz > --- > softmmu/cpus.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) Reviewed-by: Richard Henderson Queued to tcg-next. r~