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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1731363524; bh=rVXQpgZFFCB0B7kPGYqOLEcaXAM10/xQ6g5TjF+6I8U=; h=Date:From:To:Cc:Subject:Content-Type; b=grDLkr9LQDkA+yPuDhKrvqAFjSkSoQbemh7TU9yAzsCEbt/HavjkCCqOSu+/SGsF1 c6F3iBXU/wemE3/v5CADdb0D2BPELH5Ml3lBnAknCKIehRIw/+PHqyfz4mi52I2RKx bPXJNzIIig2tLo32ZhCDxlTc4Phss0WB/Y2iETBOy0An/HOJceGHNt9mwcGbbKpHUF cCrHOBfwkid7z0VNzWxahmVh2SmGY0yiEr0EqIQAVaJj4ppPVziGHgpgThkNa/8OcF PotTC2UEeyPflRyFcXg+k/jQhs3dPczUw918xn+eMN/KJQhfknwgz5hdkkuJrCGWMr HVvG+MNz3jwnQ== Date: Mon, 11 Nov 2024 14:18:39 -0800 From: Davidlohr Bueso To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 0/4] move per-vma lock into vm_area_struct Message-ID: <20241111221839.w4rqqlvvkm42jdgm@offworld> Mail-Followup-To: Suren Baghdasaryan , akpm@linux-foundation.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20241111205506.3404479-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20241111205506.3404479-1-surenb@google.com> User-Agent: NeoMutt/20220429 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EF76D40056 X-Stat-Signature: 99js47h5rqd3jg8r8bbt3ng3o5tpzrxr X-Rspam-User: X-HE-Tag: 1731363468-746593 X-HE-Meta: U2FsdGVkX190oObp+KsQpvbVKVGNRPSdVyYVApHfdtee23mwXjW6B89IXPm4zgmFqTqOxV66wPZKdo/QIGwNx6yc14ojLTZ/XQax9712ML3hlRViHkjA+ItKX3zpj1C+LJTDp2hOyKHmT58QKnosAUGTjbczax8qANW1G0eWK9azKI9KPOGM83oje/RAxQqW0LO23wuEjH7eNK3Q/RrqQVm3P0ydE6OdCXbnGtwWSKV8gdSssAylu/qqT1M+5uX3dZPWJHevDUt6YyxgX19RQKjvIbaqubCg1AmlcRmvn3U4+E0ftUsTxsO8K1Gm77EzoJltDu2mrKuiXzGmaISXqPoNWlacP4YWV//6JAVCe+ebmYgzZMRym+a10sjT26UXcK6UrgMHwO6mnu52Rqz3H2/tTSoqAqQ1RaX26m4eFT3qFApCaojAr20yD1XR2jZCx9FUy92K5vnzsaZt/EdUYxwFZ8UQPDch/EUhj5+n4O2V3Er2wdVTSepzWjpT7ittdFLitt61GfnrIiVtNUfcbEYHLefcHuEVW62mr73PmX4aobOZo8K3xKR0f8TEtBUgeYcc09MA9VLGWMfikolu6xRBsIpSKMl4awIiGRzKgDoxKcWUdYayQ09AnN+Bk7sy5SQAkpqGkK0Vvr11FwCE4QXWLEb9R6FJcGohJWjCBCCunPsxh8f29ZOwo32DtTtxe8k+3T+QKQChCfeWWFxDryEdRG1QuF6qWjl2WsQZ0kHOJs3jC0E/uI1MbajQTTEBk5G/QfY1+TzJpflaFjf+xHtB5IOVO88kE+itYZWguYwRJNzIvrvaQ6VdvF5F/9fpPQH/J7tTcX7svtlFPVaa+I88suR3ikMbWjyxeQFUAqApRgHyxPSA08KIXDfOBmjWM/7WNH3p/Lo6cH3yLKcRxQHDaA5lE0NKvzN21T1ylt84/ZolkvSnJ147yCwIYymSyht/SF0rciVKUzHNjSb yrLy5xUW PUNMQNITKcAjhg4FY3J9+R+Gn951w4TIR7kMpUIKj8spNW592hKtQ+QiXSLHxNABS7He4J1qHRgVfr6MD1IoDiyhWpQMQ4m9m6EapiYSIsm4TyV6ZBIN0BeJMki4bBFZ6UtdPhbg71AtBnbNikV7ZiF4PX5ujbDtcEO8Rqq4fMQyKSAw8yMywBNs6Vkb6hH1bUR+ei/szpNAWTGZ9vepoBxK/qOO9Ne9BxT3Qf9gepqHRYIRGm5ndfKr1aVrtZPasPNEDIOjrnghQdtRyVlf0Wo2YZ4dHbwhpmFNHzjVEjUYn3rJKuojavvhNmSNWQhK2e3hubw53czRe3GwPgsmlbG1HHg== 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 Mon, 11 Nov 2024, Suren Baghdasaryan wrote: >To minimize memory overhead, vm_lock implementation is changed from >using rw_semaphore (40 bytes) to an atomic (8 bytes) and several >vm_area_struct members are moved into the last cacheline, resulting >in a less fragmented structure: I am not a fan of building a custom lock, replacing a standard one. How much do we really care about this? rwsems are quite optimized and are known to heavily affect mm performance altogether. ... >Performance measurements using pft test on x86 do not show considerable >difference, on Pixel 6 running Android it results in 3-5% improvement in >faults per second. pft is a very micro benchmark, these results do not justify this change, imo. Thanks, Davidlohr