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charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7E73380004 X-Stat-Signature: yqie99wki5sojh4de8gc8m1mj7ths176 X-HE-Tag: 1771514920-817801 X-HE-Meta: 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 cGWAQbN9 /kmSwZyp63yWfZj3nV2G753dCb5SxwXhZ7vet/gWslLUI5PV9Qdsh4GTLHYBIOBFfawsulSTz0+X+r68Uw/y1GwDc/LnqT/oKA2A2aAcj2ZBdL0iR9N5XP1HwQ1eDOww4nfABeb+YB83FuFarQNMnBn12RFByYoo+SSS+dQ34eVXPOdXIE7ZrekQXFQYK2m0IDkE3gh3U0vZUZa00GsMmvs5kTrvlWSb83PoUXzxPxwfbVckj2FYorSfMVka+5TusOmKAsC/3FVILBRevFSiYLOIxSerM/Moe/YGGF7qYfJoKB9rT256yg1FV482OLFQu9qyqx7O3/3FbxclbhL8Ccjy+dM7UhtMaOYaCxMZLB3qublbiaW4JybBXehBSqlet55ECr3ZEASUet1M= 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, 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. > > > If CONFIG_QPW=n, or kernel boot option qpw=n, then only local_lock > > (and remote work via work_queue) is used. > > > > What "pcp book keeping activities" you refer to ? I don't see how > > moving certain activities that happen under SLUB or LRU spinlocks > > to happen before return to userspace changes things related > > to avoidance of CPU interruption ? > > Essentially delayed operations like pcp state flushing happens on return > to the userspace on isolated CPUs. No locking changes are required as > the work is still per-cpu. > > In other words the approach Frederic is working on is to not change the > locking of pcp delayed work but instead move that work into well defined > place - i.e. return to the userspace. Michal, I can't find such work from Frederic. Do you mean: Subject: Re: [PATCH v6 00/29] context_tracking,x86: Defer some IPIs until a user->kernel transition >From Valentin ? Or if you have a pointer to Frederic's work. > Btw. have you measure the impact of preempt_disbale -> spinlock on hot > paths like SLUB sheeves? Doing that, will post results as soon as possible.