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[118.211.5.80]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2c8d8060fbesm267738a91.26.2024.06.25.17.57.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Jun 2024 17:57:41 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 26 Jun 2024 10:57:36 +1000 Message-Id: Cc: "Tejun Heo" , "Peter Zijlstra" , "Lai Jiangshan" , "Srikar Dronamraju" , Subject: Re: [PATCH 0/4] Fix scalability problem in workqueue watchdog touch caused by stop_machine From: "Nicholas Piggin" To: X-Mailer: aerc 0.17.0 References: <20240625114249.289014-1-npiggin@gmail.com> <9d1d4a41-fcdb-448c-9a0f-bc9909193fa9@paulmck-laptop> In-Reply-To: <9d1d4a41-fcdb-448c-9a0f-bc9909193fa9@paulmck-laptop> On Wed Jun 26, 2024 at 12:53 AM AEST, Paul E. McKenney wrote: > On Tue, Jun 25, 2024 at 09:42:43PM +1000, Nicholas Piggin wrote: > > Here are a few patches to fix a lockup caused by very slow progress due > > to a scalability problem in workqueue watchdog touch being hammered by > > thousands of CPUs in multi_cpu_stop. Patch 2 is the fix. > >=20 > > I did notice when making a microbenchmark reproducer that the RCU call > > was actually also causing slowdowns. Not nearly so bad as the workqueue > > touch, but workqueue queueing of dummy jobs slowed down by a factor of > > several times when lots of other CPUs were making > > rcu_momentary_dyntick_idle() calls. So I did the stop_machine patches t= o > > reduce that. So those patches 3,4 are independent of the first two and > > can go in any order. > > For the series: > > Reviewed-by: Paul E. McKenney Oh, it did get a comment :) Thanks Paul. Not sure who owns the multi_cpu_stop loop, Tejun and Peter I guess but that was 10+ years ago :P I might ask Andrew if he would take patches 3-4, if there are no objections. Thanks, Nick