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AJvYcCX8zRh3N0JBAUjCyWaE+XhsuGGYa3GoY2ZHYIkwmuoCGa37cLdeDRnLPVkElppdQgB2T1YG9TJ+FA==@kvack.org X-Gm-Message-State: AOJu0YzriO7C0zIK8v686Yfn9ZeH2xcPSXxpLzwMrJaBowjUFhy8utcH IFuG3vkzB4iLYYXGQdcJiqC7bhvemvILy+wyfyjz0g1mrclZrihlx18uNpNyoDD+y0+rG/va1JZ QBO37xkQsQvg24FBx1ktW27vHfjbkE90HNIb1 X-Gm-Gg: ASbGnctbxcRF7Rb6RVHg2/wzY3RIKPdfqssySr4VAU4YR33+AlvznWW1OjoBYSVoYW+ 55Uh64/UGXgjYKSy2T0P+FYgKNP5yg9Q= X-Google-Smtp-Source: AGHT+IHOHqtu12HxKTzwQ9ea8Tgqmnl1gO3SOvsktFa3dqeLwFmRLXisS/65u0SwMQl44JLD7qB1bPGBItqFEiOgUCo= X-Received: by 2002:a05:622a:191a:b0:45f:89c:e55 with SMTP id d75a77b69052e-4652ffd2a22mr1447381cf.8.1732146790188; Wed, 20 Nov 2024 15:53:10 -0800 (PST) MIME-Version: 1.0 References: <20241120000826.335387-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 20 Nov 2024 15:52:59 -0800 Message-ID: Subject: Re: [PATCH v4 0/5] move per-vma lock into vm_area_struct To: Shakeel Butt 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, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, souravpanda@google.com, pasha.tatashin@soleen.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B6B7F80005 X-Stat-Signature: 7563ei7x63y7k7zmm9kg7eb685nfj8gp X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1732146692-381488 X-HE-Meta: U2FsdGVkX1/feE5LpTeA+uUFhOh46a1qlFIBSVVQEC4EkSTlh73mGhjjSS6u8r53WAHqOor3gxt3r/3mla4bAfO7VcGalzYQAAdSJ8xaYGMYMTDTFaRptwtFFo++ILNjFZNI4HIy/qx9hnYumWf44WZMtKcdKpMs69ZcZBU9jnDsbyhTu6yV5ESPaODsG2Hk5baQ7mhw8cuFCTjYATCwVTn3EIK+xza5ggFya1OGRSpTRibhYoU2KI8onuyVFxHNpZgM1I+NuFj3To7OX79DDcovgFDa7E1OyZO/skUF9mtwU6XT4qrig6wNKY/zVJ+vRks+Zh7A7hR+RWE49jEa/3M5pvPj5Z3GLGt74YUMrYKFEhlCtrIKRfe6yzjzKnx4S2T/mcTDrzXcKvToyWJtCi0Es+6hfvqkr2hPM0M9mSDU2fV0ph0ohUPpMakFS/rfRZWkNBt/8hyHS2xcJ2cePpEo3D5p8Nhtp4M69+eO17v5hxY6HDH6oE0ssIVvq5sB9PnpFxDt7fK/1Yt20s+i0hZp0+MlNKpvaW6HmzpJakXrtI95cr9mSo89+9NexVbHNEswcc17E7gmmV4nUDkQWrs6I6gMkssnYhdni6ZY92Je4y11730NylhOUpUash5T3dLTFIpK39ZbGSWeKpxMTdOFtwf2cJkQAXMdGqUJkiV9Ay5DMMJqu+2u3C1Z1ab5dblRvCT8GSZ27XoveNMl1wNo+4bBEr+MFopX0D2slxdO9JvCm26ZNsusden+BxfEp43mvM8ddhoqUx4/VUFpwLJmK7+Sew/nXkAjJJhVC+A7hcU3MfCLQAWKBCjG6U0vh5+TJ7/61Mf3ui7lgHMT+aPgvkCU1Wmdz7tJaQ/fGuulrCJStNVv8QJMNe3bStAQlM2B1yx2/scL+ENQ/oRUtqtc7M2SpauE2Bwq1nJt/y/vcUWaqhmMmw5IXBBwBZ1Y5CuB39T+mnfOje4wt81 eACmTJBd 4G3ZgRvF3+87Ci3WeEzOqw9PGqFCDX6xaagojaKPtTMghBaq+WMJSe/zwxXfZE8HR7KPpEI9IrZ22jQpgXWTQdtTaIk27WcHkPWvThnzBK9ynPpUH3tnEp/isq44DjOUkuc7jtTM+LDUnxj7HG0ugDf2rZo9kPC0tz72bs2ZNs4dGhBDy0WmBL5SZimyzYpZLpEZExVKrGjwAQF73w0rG5yLvG4w2uZ8jm55ubEPBPQAbLqFiYPllTnSNNg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000012, 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, Nov 20, 2024 at 2:10=E2=80=AFPM Shakeel Butt wrote: > > On Tue, Nov 19, 2024 at 04:08:21PM -0800, Suren Baghdasaryan wrote: > > Back when per-vma locks were introduces, vm_lock was moved out of > > vm_area_struct in [1] because of the performance regression caused by > > false cacheline sharing. Recent investigation [2] revealed that the > > regressions is limited to a rather old Broadwell microarchitecture and > > even there it can be mitigated by disabling adjacent cacheline > > prefetching, see [3]. > > If 'struct vm_area_struct' is prone to performance issues due to > cacheline misalignments then we should do something about the > __randomize_layout tag for it. I imagine we can identify the fields > which might be performance critical to be on same cacheline or different > cacheline due to false sharing then we can divide the fields into > different cacheline groups and fields can be __randomize_layout within > the group. WDYT? I think that's a good idea since shuffling these fields around does affect performance. I can look into it once these changes get finalized and the layout gets more stable. >