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AJvYcCWm3GsMy63yAaweVoevFL3h5DXnLP9aaWdsSFD7sjwdeANFOKzAA03WBkcPdTI02Qf7PSBBYHdb1A==@kvack.org X-Gm-Message-State: AOJu0Yx4+HSiTDcRRAj8iwMTB1qwYi5/cBP/vHGzLJ/74qwp8tmr2HCi QCT9VziiL6O8+7+aZUA5KiIjUrU/owOTSssexsGa9SlwZnPMHccpPmuVN67ieSifLRjO6jm7MMI 0yBirlqclOVFq5bZrzLxJmTY1fTgX7CLxeFB0 X-Gm-Gg: ASbGncv5sGN+zaNYg283xiapDwZ91E9m/lv5roTBSL+vkMtGDijMg4jeG1mJYCZwvJy FTOEJQPAvjtWE3kID7+uzmrj3PWsDgLHkJdGpgq9xUWoH5WzBkqo+lITH8cv976W44j2f98mY X-Google-Smtp-Source: AGHT+IHDuLV4fujynqcRkA0GndFhAYVnc8TQAi854bSzeYYHzi0RBRg+6y9hnvMQO4JUbp3yILSA8/hlwG7huDMipjM= X-Received: by 2002:a05:622a:6186:b0:466:a3ed:bde7 with SMTP id d75a77b69052e-46fc55f7d43mr2156801cf.6.1738043447748; Mon, 27 Jan 2025 21:50:47 -0800 (PST) MIME-Version: 1.0 References: <20250111042604.3230628-1-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 27 Jan 2025 21:50:36 -0800 X-Gm-Features: AWEUYZnjiIuowX4OTkjkTw9V3sA9TRsIgEZqtk51nGBoKXRYsomJkoZtqy6N6CY Message-ID: Subject: Re: [PATCH v9 00/17] reimplement per-vma lock as a refcount To: Shivank Garg Cc: akpm@linux-foundation.org, peterz@infradead.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.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, richard.weiyang@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-Stat-Signature: h3u6t78bigu1u5nuoaqbzuwab9jqd4uk X-Rspamd-Queue-Id: 005B91C0009 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1738043448-715105 X-HE-Meta: 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 JVzG0Aq+ U7Zia9JdP0zcvqTaRAzERUT4q9A414qA6udIwlX4dR8W3YF1Mkjge2JXCFrgWRisq7w6peLx6s1T8JlUAoVGN1PZwG59oC9iYTrZoJOPKw3qhT56xHFYYVavEuoNkEtYZa2oAuP2YEV+m/6pLrOCzhc5eaHkZRoBtcwHkFcPcGqGZAzS7ANUs8gO8+3b7V/IOiA9/JcWHuAiL1cnB/TxjPbHW/FaB+oJJ8w+ArXSiINVSAQFTREthBk1juNDRtgJFByTstbELiD4IAC7dAP+nE76BqOIsAxJeKeC3MI5jWKdpzlE5H3imQZUb0Y6Riba5O5Mz+kOCdNH/ySH8mjL4wcmkrXg0dGX5Exkg3FCDmCZKSG4= 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, Jan 27, 2025 at 9:27=E2=80=AFPM Shivank Garg wro= te: > > Hi Suren, > > I tested the patch-series on AMD EPYC Zen 5 system > (2-socket, 64-core per socket with SMT Enabled, 4 NUMA nodes) > using mmtests's PFT (config-workload-pft-threads) benchmark on > mm-unstable. > > On 1/11/2025 9:55 AM, 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 allow= s > > 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 un= til > > it is inserted into vma tree; > > 3. replaces vm_lock and vma->detached flag with a reference counter; > > 4. regroups vm_area_struct members to fit them into 3 cachelines; > > 5. changes vm_area_struct cache to SLAB_TYPESAFE_BY_RCU to allow for th= eir > > 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= %* > > Results: > mm-unstable-vanilla mm-unstable-v9-pervma-= lock > Hmean faults/cpu-1 2018530.3023 ( 0.00%) 2051456.8039 ( 1.63%= ) > Hmean faults/cpu-4 718869.0234 ( 0.00%) 720985.6986 ( 0.29%= ) > Hmean faults/cpu-7 377965.1187 ( 0.00%) 368305.2802 ( -2.56%= ) > Hmean faults/cpu-12 215502.5334 ( 0.00%) 212764.0061 ( -1.27%= ) > Hmean faults/cpu-21 149946.1873 ( 0.00%) 150688.2173 ( 0.49%= ) > Hmean faults/cpu-30 142379.7863 ( 0.00%) 143677.5012 ( 0.91%= ) > Hmean faults/cpu-48 139625.5003 ( 0.00%) 156217.1383 * 11.88%= * > Hmean faults/cpu-79 119093.6132 ( 0.00%) 140501.1787 * 17.98%= * > Hmean faults/cpu-110 102446.6879 ( 0.00%) 114128.7155 ( 11.40%= ) > Hmean faults/cpu-128 96640.4022 ( 0.00%) 109474.8875 ( 13.28%= ) > Hmean faults/sec-1 2018197.4666 ( 0.00%) 2051119.1375 ( 1.63%= ) > Hmean faults/sec-4 2853494.9619 ( 0.00%) 2865639.8350 ( 0.43%= ) > Hmean faults/sec-7 2631049.4283 ( 0.00%) 2564037.1696 ( -2.55%= ) > Hmean faults/sec-12 2570378.4204 ( 0.00%) 2540353.2525 ( -1.17%= ) > Hmean faults/sec-21 3018640.3933 ( 0.00%) 3014396.9773 ( -0.14%= ) > Hmean faults/sec-30 4150723.9209 ( 0.00%) 4167550.4070 ( 0.41%= ) > Hmean faults/sec-48 6459327.6559 ( 0.00%) 7217660.4385 * 11.74%= * > Hmean faults/sec-79 8977397.1421 ( 0.00%) 10695351.6214 * 19.14%= * > Hmean faults/sec-110 10590055.2262 ( 0.00%) 12309035.9250 ( 16.23%= ) > Hmean faults/sec-128 11448246.6485 ( 0.00%) 13554648.3823 ( 18.40%= ) Hi Shivank, Thank you for providing more test results! This looks quite good! > > Please add my: > Tested-by: Shivank Garg > > I would be happy to test future versions if needed. That would be very much appreciated! I'll CC you on the next version. Thanks, Suren. > > Thanks, > Shivank > > > > > > > Changes since v8 [4]: > > - Change subject for the cover letter, per Vlastimil Babka > > - Added Reviewed-by and Acked-by, per Vlastimil Babka > > - Added static check for no-limit case in __refcount_add_not_zero_limit= ed, > > per David Laight > > - Fixed vma_refcount_put() to call rwsem_release() unconditionally, > > per Hillf Danton and Vlastimil Babka > > - Use a copy of vma->vm_mm in vma_refcount_put() in case vma is freed f= rom > > under us, per Vlastimil Babka > > - Removed extra rcu_read_lock()/rcu_read_unlock() in vma_end_read(), > > per Vlastimil Babka > > - Changed __vma_enter_locked() parameter to centralize refcount logic, > > per Vlastimil Babka > > - Amended description in vm_lock replacement patch explaining the effec= ts > > of the patch on vm_area_struct size, per Vlastimil Babka > > - Added vm_area_struct member regrouping patch [5] into the series > > - Renamed vma_copy() into vm_area_init_from(), per Liam R. Howlett > > - Added a comment for vm_area_struct to update vm_area_init_from() when > > adding new members, per Vlastimil Babka > > - Updated a comment about unstable src->shared.rb when copying a vma in > > vm_area_init_from(), per Vlastimil Babka > > > > [1] https://lore.kernel.org/all/20230227173632.3292573-34-surenb@google= .com/ > > [2] https://lore.kernel.org/all/ZsQyI%2F087V34JoIt@xsang-OptiPlex-9020/ > > [3] https://lore.kernel.org/all/CAJuCfpEisU8Lfe96AYJDZ+OM4NoPmnw9bP53cT= _kbfP_pR+-2g@mail.gmail.com/ > > [4] https://lore.kernel.org/all/20250109023025.2242447-1-surenb@google.= com/ > > [5] https://lore.kernel.org/all/20241111205506.3404479-5-surenb@google.= com/ > > > > Patchset applies over mm-unstable after reverting v8 > > (current SHA range: 235b5129cb7b - 9e6b24c58985) > > > > Suren Baghdasaryan (17): > > 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: introduce vma_iter_store_attached() to use with attached vmas > > mm: mark vmas detached upon exit > > 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: move lesser used vma_area_struct members into the last cacheline > > mm/debug: print vm_refcnt state when dumping the vma > > mm: remove extra vma_numab_state_init() call > > 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 | 156 ++++++++++++++++++++++------- > > include/linux/mm_types.h | 75 +++++++------- > > include/linux/mmap_lock.h | 6 -- > > include/linux/rcuwait.h | 13 +-- > > include/linux/refcount.h | 24 ++++- > > include/linux/slab.h | 6 -- > > include/linux/types.h | 12 +++ > > kernel/fork.c | 129 +++++++++++------------- > > mm/debug.c | 12 +++ > > mm/init-mm.c | 1 + > > mm/memory.c | 97 ++++++++++++++++-- > > mm/mmap.c | 3 +- > > mm/userfaultfd.c | 32 +++--- > > mm/vma.c | 23 ++--- > > mm/vma.h | 15 ++- > > tools/testing/vma/linux/atomic.h | 5 + > > tools/testing/vma/vma_internal.h | 93 ++++++++--------- > > 18 files changed, 465 insertions(+), 281 deletions(-) > > >