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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id r5sm15580612wrw.96.2021.05.18.05.30.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 May 2021 05:30:05 -0700 (PDT) Subject: Re: [PATCH 2/3] ci: do not use #processors+1 jobs, #processors is enough To: Thomas Huth , qemu-devel@nongnu.org References: <20210518084139.97957-1-pbonzini@redhat.com> <20210518084139.97957-3-pbonzini@redhat.com> <40f9d46b-d234-c029-3ba2-f5dcac8b87fc@redhat.com> From: Paolo Bonzini Message-ID: <7155c55a-1566-d7f0-d59e-ee48707302cf@redhat.com> Date: Tue, 18 May 2021 14:30:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <40f9d46b-d234-c029-3ba2-f5dcac8b87fc@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.374, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alex.bennee@linaro.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 18/05/21 12:49, Thomas Huth wrote: >> >> -    - JOBS=$(expr $(nproc) + 1) >> +    - JOBS=$(nproc || echo 1) > > The basic idea of the "+ 1" was to make sure that there is always a > thread that runs on a CPU while maybe another one is waiting for I/O to > complete. Ah, I see. It doesn't make much sense for "make check" jobs however, which is where I wanted to get with the next patch. I'm not sure it's even true anymore with current build machines (which tend to have a large buffer cache for headers) and optimizing compilers that compilation is I/O bound, so I'll time the two and see if there is an actual difference. Paolo This is suggested by various sites on the web, e.g.: > > https://unix.stackexchange.com/questions/519092/what-is-the-logic-of-using-nproc-1-in-make-command > > So not sure whether this patch here make sense ... I'd rather drop it.