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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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