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Tue, 21 Jan 2020 13:19:34 -0800 (PST) X-Google-Smtp-Source: APXvYqxoPnkxLxUGe7WRD6VylEoIv+x6W5+cow3h5Z9Uz8mj37YpcfxZ7pVN18YIIyxft0zVUg14Tg== X-Received: by 2002:a5d:6a02:: with SMTP id m2mr7108137wru.52.1579641574308; Tue, 21 Jan 2020 13:19:34 -0800 (PST) Received: from x1.bristot.me ([83.136.205.253]) by smtp.gmail.com with ESMTPSA id v22sm872400wml.11.2020.01.21.13.19.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 13:19:33 -0800 (PST) Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA To: Peter Zijlstra , Alex Kogan References: <20191230194042.67789-1-alex.kogan@oracle.com> <20191230194042.67789-5-alex.kogan@oracle.com> <20200121132949.GL14914@hirez.programming.kicks-ass.net> <20200121135034.GA14946@hirez.programming.kicks-ass.net> From: Daniel Bristot de Oliveira Message-ID: Date: Tue, 21 Jan 2020 22:19:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200121135034.GA14946@hirez.programming.kicks-ass.net> Content-Language: en-US X-MC-Unique: pYP9aLwFMPaf7UKeemBSpw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200121_132136_528185_7191DB99 X-CRM114-Status: GOOD ( 13.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, guohanjun@huawei.com, arnd@arndb.de, dave.dice@oracle.com, jglauber@marvell.com, x86@kernel.org, will.deacon@arm.com, linux@armlinux.org.uk, steven.sistare@oracle.com, linux-kernel@vger.kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, longman@redhat.com, tglx@linutronix.de, daniel.m.jordan@oracle.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 1/21/20 2:50 PM, Peter Zijlstra wrote: > On Tue, Jan 21, 2020 at 02:29:49PM +0100, Peter Zijlstra wrote: >> On Mon, Dec 30, 2019 at 02:40:41PM -0500, Alex Kogan wrote: >> >>> +/* >>> + * Controls the threshold for the number of intra-node lock hand-offs before >>> + * the NUMA-aware variant of spinlock is forced to be passed to a thread on >>> + * another NUMA node. By default, the chosen value provides reasonable >>> + * long-term fairness without sacrificing performance compared to a lock >>> + * that does not have any fairness guarantees. The default setting can >>> + * be changed with the "numa_spinlock_threshold" boot option. >>> + */ >>> +int intra_node_handoff_threshold __ro_after_init = 1 << 16; >> There is a distinct lack of quantitative data to back up that >> 'reasonable' claim there. >> >> Where is the table of inter-node latencies observed for the various >> values tested, and on what criteria is this number deemed reasonable? >> >> To me, 64k lock hold times seems like a giant number, entirely outside >> of reasonable. > Daniel, IIRC you just did a paper on constructing worst case latencies > from measuring pieces. Do you have data on average lock hold times? > I am still writing the paper, but I do not have the (avg) lock times. It is it is in the TODO list, though! -- Daniel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel