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[109.81.83.241]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4834d5e0ed5sm130603715e9.5.2026.02.11.09.07.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Feb 2026 09:07:18 -0800 (PST) Date: Wed, 11 Feb 2026 18:07:17 +0100 From: Michal Hocko To: Marcelo Tosatti Cc: Vlastimil Babka , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Leonardo Bras , Thomas Gleixner , Waiman Long , Boqun Feng , Frederic Weisbecker Subject: Re: [PATCH 0/4] Introduce QPW for per-cpu operations Message-ID: References: <20260206143430.021026873@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D8D9DA0012 X-Stat-Signature: 3hgraa7mo7kpfhyss95wbmnq6bgw9z3w X-HE-Tag: 1770829640-129840 X-HE-Meta: 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 pnZzVGL5 9yFrn/MKEbptaRxAKvkwN1x8WaEtAMEPBjMXF6YQQ8bnul3rjgigD0sjHDvGrW0fB46xUAFjsoswXON0Y1SN6BfhKUyyNgBOTDu4/eqVSwCh8k4QTDlWUwaA1/xX1+oCRTbBfOrounYYkcoxOvalNwVcWP+AT2jTxsLI/Wk8RHhcm6lAcyudJMkaPk8qCzDGa9ZJf4Z3VTHftXsz9EYUrwtvMwg7JEmUmfpjiOjFKuJzd2i2wJ+VDRXrKcNQ1/pFQ70S6gEjLdiqD8IgwkkpJpxRYG3feuVqD0Q5j4G41Z5UwvXnhwQUyYK7PetbJhyNV63bCcbdUB4jsxkIQ4xeF6VUUHWCsrF89yrHdFuVgpDnSo81/RlDrsStEKshK/Ucz5JaoDdZynbTCKBWnZcQR1jN/0HnYG9hM/w2xdJzygotzmME= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed 11-02-26 13:50:45, Marcelo Tosatti wrote: > On Wed, Feb 11, 2026 at 05:38:47PM +0100, Michal Hocko wrote: > > On Wed 11-02-26 09:01:12, Marcelo Tosatti wrote: > > > On Tue, Feb 10, 2026 at 03:01:10PM +0100, Michal Hocko wrote: > > [...] > > > > What about !PREEMPT_RT? We have people running isolated workloads and > > > > these sorts of pcp disruptions are really unwelcome as well. They do not > > > > have requirements as strong as RT workloads but the underlying > > > > fundamental problem is the same. Frederic (now CCed) is working on > > > > moving those pcp book keeping activities to be executed to the return to > > > > the userspace which should be taking care of both RT and non-RT > > > > configurations AFAICS. > > > > > > Michal, > > > > > > For !PREEMPT_RT, _if_ you select CONFIG_QPW=y, then there is a kernel > > > boot option qpw=y/n, which controls whether the behaviour will be > > > similar (the spinlock is taken on local_lock, similar to PREEMPT_RT). > > > > My bad. I've misread the config space of this. > > My bad, actually. Its only CONFIG_QPW on the current patchset. Yeah. PREEMPT_RT -> CONFIG_QPW=y and cmd line makes no difference -- Michal Hocko SUSE Labs