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b=UZ47fYzbLzv5Twpl9VBd5KCJKi2y9/sKpLbv6GEne7E5LtfMtUy01KGn7gYsLx77Q NjqSJdMwdQcvnwse/iC/an96fMLUMOfvDcI8XdXvaTcp03FhWUORUWHq8rNBjVWYff pBE9IGsAKkJAdSPcTgiQ7RHBaJoEWnOhzQtewGgFppIP49YEv2+09HMeC+0Hz8sFAL z5eXLened+BzuY1aiIEu2mEl0ql8Ryqx5rfse1okUbGzH3AiOcnS16dV/iULqa6gZl VBhT6cjcBaLLLbmVjYIv/u4wnSrcSIhZnGrk7eviNXvWqeVf7pQkliEYQFCJe1iwTx nRzx/fJ4XY3fg== Message-ID: <26662caf-de09-4f13-b374-dc7f879b7829@kernel.org> Date: Wed, 11 Mar 2026 08:58:05 +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-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 94072A0004 X-Stat-Signature: 7bugu13rmtpyr7iuoksq68xuf7qhi5n8 X-HE-Tag: 1773215891-863561 X-HE-Meta: U2FsdGVkX18ZhFg8ajTzoe08eTlpsc0y3MrQFYOOgrmqdmsSyfB9RpDCG9TvkHABSeBU4HPe6tSaZldYcPsT3yjN2O1ygGQgOu/4cAo6WIiYJsDAbLBeWXseIIJwtFfTRbUt/PRWihEnyk6dQ5J8279t0iz+a8NGg3tc3/B+kUhDN1VnfaG6CR5lHNQ1mowHTmccTIi2Vi59d9ONsbItLguS7xoLgk9V7jXLFnwWPGuSwSl+xQGn09Yo2wWlzo5btMhkMYNQazy7eRsSX+/lQY3FlTwQ+BGx6Z4qwfT7jq5BH3TZSJcc3kHm/RN+0IjzLXJBdtO0AwEoUFI4XS2GHO9R5BmNgxrdDYPJfB9+Jb3wQ7n3mdsnTT+4juJlB6LtcqJ4ghk6MOmGgnpUL5R67YzbFpv/D2TYclC6tMx80ZpkNS6c6upQs9HCpI+DT3l6yrUwoLmd0LR1eH0njYpOxkAFuzyQS1hsqs4bvvEOeqvL/nVVwhAOpj8SN3DArcfW+gWNyHrMe3x+3E8BndQQ2JSghl7X/18uZIXsLCFXMo638QRiJeK/w/aJFhvPxPA+n8sC9h11YAcyP43mY8Q8QbS2hG4aLPUK5b24zjIRkAlMRAiW8f7PSzX5oK3UC4OLwfVpislZXJKRduX8S3HOdj69GylvNfTWN3s476ToIx1DKgbvBl6VPjNnOX8HIA2lzxEMZ999JpC9ftLbFLI0JcnxObKX5GH06BWS3oOwf+UHTyTjAfmsNe+kvfwnaDbuQcaVkpWdzAbivse+mzqp4rNK4pja9GGS0CNE7ZYyqPKbGnlS99ym84B3W9YmDsWvrmjNzZyMcWPfxxkmpRdZrsJplT+WldNot2D+hon4hKiiAcowkx/kpFC96+q3P9OAATpXB1NfmKV3GoQ1DYeNBZIat3MGcN19O+NjnaIBJCEPNf14mw8c1pTAPGBCqM/RLrxzcJ9jaFehKEaWjS2 ss3CAn3J L8JTJW9P6NUwZ/Qzs8hlUY3d6LRIQxOLVEOd7TRewCQ3pIg5g3veAnN6gSLWcpziWOuvBlPyAxUEJT9MV143fkHtdgh+XTXGNPyCpwH4l1P+k2HpXfsrV8z/CYGVIw/+AEk3ZV+HGR5l95AEYng+hNg6BS+vTWjS8nvZ1ByCBlKHNE7u66Jvjq5kioDw11+bYIq328/NjUUVX/IMgGag5Ztr94AYckA4sDUtHBVKhbKTx5eJhfJWpnGWGMwxvzsIXv6da72ygblIOJdcvu1dSK3a/1l5Ux3MNh8cpl61Ant/ESYSedP7oN/38stgJPrgl3PJAc3FBKTcAjrjd3sr9bgN3jRE2u7saCHaGhfJc4Uq7JRe0FNfx+5NqdKeplArsLDLU 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: > Index: linux/Documentation/admin-guide/kernel-parameters.txt > =================================================================== > --- linux.orig/Documentation/admin-guide/kernel-parameters.txt > +++ linux/Documentation/admin-guide/kernel-parameters.txt > @@ -2840,6 +2840,16 @@ Kernel parameters > > The format of is described above. > > + qpw= [KNL,SMP] Select a behavior on per-CPU resource sharing > + and remote interference mechanism on a kernel built with > + CONFIG_QPW. > + Format: { "0" | "1" } > + 0 - local_lock() + queue_work_on(remote_cpu) > + 1 - spin_lock() for both local and remote operations > + > + Selecting 1 may be interesting for systems that want > + to avoid interruption & context switches from IPIs. Requiring a new boot option is always a nuissance. The cpu isolation is AFAIK difficult enough to setup already. Could the default be that qpw will auto-enable if there are isolated cpus configured? The option could still be useful for overriding that automatic decision to both 0 and 1 for testing etc, but not requried for the expected usecase?