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b=MJ5h64pRkNG7MTzmGfVUhEpIvCfLRPdDgZ+HBzr29YTlo8RuYyVEPMMwkfVPI7+tG DY1ce4MaKdmhWCcIeatCWo8nvAPDXexyLB/zjS+E+887Bp66ZOG4+I0bWDVY1EZCgO 6r01gWnEeqNknfBJGzMn50z0Z+zcnOsY83IHmFxMNZIo2mrOd9wEL2j9z9YgoYSZQ3 UAMDbSi+dLK/RX/lvyeXRmMo3+cobEko0BPtYh5rm1n/kGZDM2I2g9/KtJvovKaXPz Lce/xR+FgMd955QsHqTOEgDRroEfGcu5W7dZaVP4qGSpdn7vjiB+JFBo/So/MdMHDe Jf9wjqOSdajWw== Message-ID: <682380ba-c8f3-4023-928c-2152e934f8db@kernel.org> Date: Tue, 3 Mar 2026 13:03:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] Introducing qpw_lock() and per-cpu queue & flush work Content-Language: en-US To: Marcelo Tosatti , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Johannes Weiner , Michal Hocko , 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 Feun , Frederic Weisbecker References: <20260302154945.143996316@redhat.com> <20260302155105.214878062@redhat.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20260302155105.214878062@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0985416000F X-Stat-Signature: 8ykkpttp4bkfgs5m3k6hebfoxj8a3mt3 X-Rspam-User: X-HE-Tag: 1772539422-155983 X-HE-Meta: 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 1DBWTicf xs13Q9c8hmHTVneTOMK+Wq1JdeaEJXg16PLGG5vb/89/89i1Bk8b8/ZPl1vb63gRCl8PnocXhUG0iRS2CveHOlhh6KopTz9n1fE1xNNDMCdLSgrWTLr0X4RaETS/bDA/V0ZZukg8maQcpE6+FLM2Nm8HlQ8ZLS67CLWnPPNMzYl3+jFkO68DdPogdm8qlpZh/t/yUMqtobKJx7p9Q61iXpliZb8vSNNxaGebnQZs177BdRIZB7JYhcpOqiowUXaaxuJwGA/BAuDd15KOKOElXaYAGYI/IDDt180gFtD1wEnzTDQcvyh8c4oQTBKxn+iVd5ZaFOyvx69AvuwvpI/cvQYPYj/vgRt1r2POwiY6waZqHer5UlSyPsjgCecKhJ3plIBbE Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 16:49, Marcelo Tosatti wrote: > +#define local_qpw_lock(lock) \ > + do { \ > + if (static_branch_maybe(CONFIG_QPW_DEFAULT, &qpw_sl)) { \ > + migrate_disable(); \ Have you considered using migrate_disable() on PREEMPT_RT and preempt_disable() on !PREEMPT_RT since it's cheaper? It's what the pcp locking in mm/page_alloc.c does, for that reason. It should reduce the overhead with qpw=1 on !PREEMPT_RT. > + spin_lock(this_cpu_ptr(lock.sl)); \ > + } else \ > + local_lock(lock.ll); \ > + } while (0) > +