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AJvYcCWVZmMFmi4gQJaTkDxAfifxHso1DatEZrPpESO6ECfxNzQRV0rmgHsAPLlatTA065YoaM+KJcf3PQ==@kvack.org X-Gm-Message-State: AOJu0YwtNlkNk/HsGy1sQjTgROtvqzjKijMi3DqGdQBTa0CJPXl7BQkU 6Vx+PNgu5d6zHhNlp9Rh3z4UKMjENPMq19Qzn94RMBpLAz4dgeq5Q7XLL1CXJrdDrsY8KbKBT03 pOcQA1pPJnaqY0bV3oiavzbNFpHCEODVvHAlzyMBDKD/20r2FzPan X-Gm-Gg: ASbGncvIH9G8odNEegn0Pf9lI4qvoofWdTGwAjhILDJupksmUGgVzXkNqWnYiEnSHod 0S9tJ/P/EoSrjN/Cvqf70Upj/fcRdlopopKTgqg== X-Google-Smtp-Source: AGHT+IFH/hDXA3VN4NX+G7/8PqmoGlyT+OXmmeRMbT/6WrJVGm8SJlGtE8wzNFYlrPKuNcV05CkFmEAczwuPhwwbWOI= X-Received: by 2002:ac8:7d92:0:b0:461:3311:8986 with SMTP id d75a77b69052e-468f979bbc4mr380911cf.18.1734377967323; Mon, 16 Dec 2024 11:39:27 -0800 (PST) MIME-Version: 1.0 References: <20241216192419.2970941-1-surenb@google.com> In-Reply-To: <20241216192419.2970941-1-surenb@google.com> From: Suren Baghdasaryan Date: Mon, 16 Dec 2024 11:39:16 -0800 Message-ID: Subject: Re: [PATCH v6 00/16] move per-vma lock into vm_area_struct To: akpm@linux-foundation.org Cc: peterz@infradead.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, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.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-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: E7F42140022 X-Stat-Signature: z7k83tckddg5f96mgb65c1bbu63uj7sr X-HE-Tag: 1734378292-439364 X-HE-Meta: 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 c1WGplbd CVtoJpND2vrLNfYDZR/L0+XSGXu+nppZZXWgjwPABpfhBIP4cEUR/YAuBqB9W7CwSStuzP13fKIjOjAoleT/ZWCScugHKdRx5Yz0FhHbH3QDlEMFW5ZnvP3ObBM+FSP5AMv5cltGVsPyIa1ZLL8OQbqdUwG1rXo8ZFPtzUqlJW4Z0Hfbn9ndLhZFZOxszaTdd9V7Ps/puNIj/13jzZHIAIRh/S0vOuJClFWIi0+fzrSQsAfOJ1KPCTAMsGwaznLCoZGUESp2PqgkamfZ2OSMLYqeNGgvnk2bwG27VU/Zt2e5QtVVEshL0GSBMDg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000057, 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, Dec 16, 2024 at 11:24=E2=80=AFAM 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]. > Splitting single logical structure into multiple ones leads to more > complicated management, extra pointer dereferences and overall less > maintainable code. When that split-away part is a lock, it complicates > things even further. With no performance benefits, there are no reasons > for this split. Merging the vm_lock back into vm_area_struct also allows > vm_area_struct to use SLAB_TYPESAFE_BY_RCU later in this patchset. > This patchset: > 1. moves vm_lock back into vm_area_struct, aligning it at the cacheline > boundary and changing the cache to be cacheline-aligned to minimize > cacheline sharing; > 2. changes vm_area_struct initialization to mark new vma as detached unti= l > it is inserted into vma tree; > 3. replaces vm_lock and vma->detached flag with a reference counter; > 4. changes vm_area_struct cache to SLAB_TYPESAFE_BY_RCU to allow for thei= r > reuse and to minimize call_rcu() calls. > > Pagefault microbenchmarks show performance improvement: > Hmean faults/cpu-1 507926.5547 ( 0.00%) 506519.3692 * -0.28%* > Hmean faults/cpu-4 479119.7051 ( 0.00%) 481333.6802 * 0.46%* > Hmean faults/cpu-7 452880.2961 ( 0.00%) 455845.6211 * 0.65%* > Hmean faults/cpu-12 347639.1021 ( 0.00%) 352004.2254 * 1.26%* > Hmean faults/cpu-21 200061.2238 ( 0.00%) 229597.0317 * 14.76%* > Hmean faults/cpu-30 145251.2001 ( 0.00%) 164202.5067 * 13.05%* > Hmean faults/cpu-48 106848.4434 ( 0.00%) 120641.5504 * 12.91%* > Hmean faults/cpu-56 92472.3835 ( 0.00%) 103464.7916 * 11.89%* > Hmean faults/sec-1 507566.1468 ( 0.00%) 506139.0811 * -0.28%* > Hmean faults/sec-4 1880478.2402 ( 0.00%) 1886795.6329 * 0.34%* > Hmean faults/sec-7 3106394.3438 ( 0.00%) 3140550.7485 * 1.10%* > Hmean faults/sec-12 4061358.4795 ( 0.00%) 4112477.0206 * 1.26%* > Hmean faults/sec-21 3988619.1169 ( 0.00%) 4577747.1436 * 14.77%* > Hmean faults/sec-30 3909839.5449 ( 0.00%) 4311052.2787 * 10.26%* > Hmean faults/sec-48 4761108.4691 ( 0.00%) 5283790.5026 * 10.98%* > Hmean faults/sec-56 4885561.4590 ( 0.00%) 5415839.4045 * 10.85%* > > Changes since v5 [4] > - Added Reviewed-by, per Vlastimil Babka; > - Added replacement of vm_lock and vma->detached flag with vm_refcnt, > per Peter Zijlstra and Matthew Wilcox > - Marked vmas detached during exit_mmap; > - Ensureed vmas are in detached state before they are freed; > - Changed SLAB_TYPESAFE_BY_RCU patch to not require ctor, leading to a > much simpler code; > - Removed unnecessary patch [5] > - Updated documentation to reflect changes to vm_lock; > > Patchset applies over mm-unstable after reverting v5 of this patchset [4] > (currently 687e99a5faa5-905ab222508a) ^^^ Please be aware of this if trying to apply to a branch. mm-unstable contains an older version of this patchset which needs to be reverted before this one can be applied. > > [1] https://lore.kernel.org/all/20230227173632.3292573-34-surenb@google.c= om/ > [2] https://lore.kernel.org/all/ZsQyI%2F087V34JoIt@xsang-OptiPlex-9020/ > [3] https://lore.kernel.org/all/CAJuCfpEisU8Lfe96AYJDZ+OM4NoPmnw9bP53cT_k= bfP_pR+-2g@mail.gmail.com/ > [4] https://lore.kernel.org/all/20241206225204.4008261-1-surenb@google.co= m/ > [5] https://lore.kernel.org/all/20241206225204.4008261-6-surenb@google.co= m/ > > Suren Baghdasaryan (16): > mm: introduce vma_start_read_locked{_nested} helpers > mm: move per-vma lock into vm_area_struct > mm: mark vma as detached until it's added into vma tree > mm/nommu: fix the last places where vma is not locked before being > attached > types: move struct rcuwait into types.h > mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail > mm: move mmap_init_lock() out of the header file > mm: uninline the main body of vma_start_write() > refcount: introduce __refcount_{add|inc}_not_zero_limited > mm: replace vm_lock and detached flag with a reference count > mm: enforce vma to be in detached state before freeing > mm: remove extra vma_numab_state_init() call > mm: introduce vma_ensure_detached() > mm: prepare lock_vma_under_rcu() for vma reuse possibility > mm: make vma cache SLAB_TYPESAFE_BY_RCU > docs/mm: document latest changes to vm_lock > > Documentation/mm/process_addrs.rst | 44 ++++---- > include/linux/mm.h | 162 +++++++++++++++++++++++------ > include/linux/mm_types.h | 37 ++++--- > include/linux/mmap_lock.h | 6 -- > include/linux/rcuwait.h | 13 +-- > include/linux/refcount.h | 20 +++- > include/linux/slab.h | 6 -- > include/linux/types.h | 12 +++ > kernel/fork.c | 88 ++++------------ > mm/init-mm.c | 1 + > mm/memory.c | 75 +++++++++++-- > mm/mmap.c | 8 +- > mm/nommu.c | 2 + > mm/userfaultfd.c | 31 +++--- > mm/vma.c | 15 ++- > mm/vma.h | 4 +- > tools/testing/vma/linux/atomic.h | 5 + > tools/testing/vma/vma_internal.h | 96 +++++++++-------- > 18 files changed, 378 insertions(+), 247 deletions(-) > > -- > 2.47.1.613.gc27f4b7a9f-goog >