From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 14E521E9060 for ; Mon, 11 Nov 2024 20:55:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731358512; cv=none; b=cyszM1FepapUsFLcAdNv+KweiXwqKKGswsUr2Lpq3a6Qyi2kvvOg5DC27aK6ozFbeIqnEJW93Io1ihhg8rdurdhNwBmdtrQtqYzk/mjrMU+um9nc5waj1Wgu3VHboosM6ihUjLFS37inEVihD0hPCvqnw6FTOP661rWOKyeaUG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731358512; c=relaxed/simple; bh=/843rvSVp64ub5KwdEW9t5Mo++sK7i8m9eZu/NNp2Xk=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=kLO8E08SSAB4x7Seb32OwKPaV2NwGh7/332rvd6oaXAACgIriHobQRjacHhX6zxsNDdMqzv1XWYFyjhXxOhqdt/FkBaYZNdRja/9IyYRvQaXoPjKSz+UOMWR2Y9w4XFt7E1VVBjqymdGTIJ2Usqftxs8cYHXBHymz408kda4KBU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kAvGE5Qw; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kAvGE5Qw" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-6eae6aba72fso52868217b3.2 for ; Mon, 11 Nov 2024 12:55:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1731358510; x=1731963310; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=YmP4q8GO3tnMB8ElYnP0I9LFxs+1Dml5N/4bHnS7ye8=; b=kAvGE5QwnSxL8++g+0E7Z2eMCV77dydiw379tIsauumD5/gAs6ypOZOIePAYJJHU0/ kZS3rz1YqXU3ZUAnYOEtNGIfPmLGW4mrm8OJWi37R8p0anmvz6ZnHs7Bf5Xf+09sOMDX 0MF5sDd++IdtcxSmvbOmToqS03q0qsWjCCIjGsTozHXon+TCtnf468g26sXXIm19vNfl 6NpjlXZafb3kvSoKJXZZCoN5vfI+ra4I5E+LogcHmb8ib8g/tesugtvGP3uiasXvTpyn IAzYVl80nIzdUHT19v6uehV8i5G/yOzGGFqqskmNjVFrbh2DUxuFxjLZjkdLPByUCPxM LItQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731358510; x=1731963310; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=YmP4q8GO3tnMB8ElYnP0I9LFxs+1Dml5N/4bHnS7ye8=; b=Gd8rIWbr9EH/yTimUGJjhnaEKzKDP+8avlo8OLgNGTxnQ+mEpYzpjcKHEmV4xdLFOv YcgkMc8kshtcyAXCWARV5Gh3PK2UDN2+A8cHvz2T9otCCYf0bogIkLoxXy5h8l23rMcT ac/xcw70VejemGuR8VJ1r7eQAvbT3bJhdgHIYsrEqIPCeldkEjVurw2/+QNbL5p0biGR js7pwnvNJbt1Bscy0X853eYZPWFQlX4n2wwKb9+Y9YkJj9nbRgAI+tum2srR//+t/QiB Zz00+3Rzlp0ScINsfMS9gtBXQn3ZAQcM9vICVCegnA/sPVoujVQ4Fqh6PNG5I8WfyBUX BnAg== X-Forwarded-Encrypted: i=1; AJvYcCW7relIsgAsp326GOyAp0SNwBYGLkZUixUNltsDW+/EpbPvAA1u1uw6VKZ7iBqHue94wcFmXWg4vwdxuNM=@vger.kernel.org X-Gm-Message-State: AOJu0Yy94/46+P0rskBr6jT9fXsXzT86hHhjWv35lzBeiAAYhnKo7+mU 8vBE1Q+BCcdO+qJKzFme5AQEMKhD+5tQGV5TYzMOtZw03HR/TxomT+UKMQaFjiYlXTLerZNVfis Vkg== X-Google-Smtp-Source: AGHT+IE8wqP80TXUer3yViZvMPgjxLtInm9y/wNhiXq5ErcsTHmSfYSHmgVvG+YL2RzGuqwNIra/g+r9+7k= X-Received: from surenb-desktop.mtv.corp.google.com ([2a00:79e0:2e3f:8:53af:d9fa:522d:99b1]) (user=surenb job=sendgmr) by 2002:a25:dc4a:0:b0:e25:5cb1:77d8 with SMTP id 3f1490d57ef6-e337f8ed8bbmr10011276.6.1731358509875; Mon, 11 Nov 2024 12:55:09 -0800 (PST) Date: Mon, 11 Nov 2024 12:55:02 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.47.0.277.g8800431eea-goog Message-ID: <20241111205506.3404479-1-surenb@google.com> Subject: [PATCH 0/4] move per-vma lock into vm_area_struct From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: 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, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" 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]. This patchset moves vm_lock back into vm_area_struct, aligning it at the cacheline boundary and changing the cache to be cache-aligned as well. This causes VMA memory consumption to grow from 160 (vm_area_struct) + 40 (vm_lock) bytes to 256 bytes: slabinfo before: ... : ... vma_lock ... 40 102 1 : ... vm_area_struct ... 160 51 2 : ... slabinfo after moving vm_lock: ... : ... vm_area_struct ... 256 32 2 : ... Aggregate VMA memory consumption per 1000 VMAs grows from 50 to 64 pages, which is 5.5MB per 100000 VMAs. 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: struct vm_area_struct { union { struct { long unsigned int vm_start; /* 0 8 */ long unsigned int vm_end; /* 8 8 */ }; /* 0 16 */ struct callback_head vm_rcu ; /* 0 16 */ } __attribute__((__aligned__(8))); /* 0 16 */ struct mm_struct * vm_mm; /* 16 8 */ pgprot_t vm_page_prot; /* 24 8 */ union { const vm_flags_t vm_flags; /* 32 8 */ vm_flags_t __vm_flags; /* 32 8 */ }; /* 32 8 */ bool detached; /* 40 1 */ /* XXX 3 bytes hole, try to pack */ unsigned int vm_lock_seq; /* 44 4 */ struct list_head anon_vma_chain; /* 48 16 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct anon_vma * anon_vma; /* 64 8 */ const struct vm_operations_struct * vm_ops; /* 72 8 */ long unsigned int vm_pgoff; /* 80 8 */ struct file * vm_file; /* 88 8 */ void * vm_private_data; /* 96 8 */ atomic_long_t swap_readahead_info; /* 104 8 */ struct mempolicy * vm_policy; /* 112 8 */ /* XXX 8 bytes hole, try to pack */ /* --- cacheline 2 boundary (128 bytes) --- */ struct vma_lock vm_lock (__aligned__(64)); /* 128 4 */ /* XXX 4 bytes hole, try to pack */ struct { struct rb_node rb (__aligned__(8)); /* 136 24 */ long unsigned int rb_subtree_last; /* 160 8 */ } __attribute__((__aligned__(8))) shared; /* 136 32 */ struct vm_userfaultfd_ctx vm_userfaultfd_ctx; /* 168 0 */ /* size: 192, cachelines: 3, members: 17 */ /* sum members: 153, holes: 3, sum holes: 15 */ /* padding: 24 */ /* forced alignments: 3, forced holes: 2, sum forced holes: 12 */ } __attribute__((__aligned__(64))); Memory consumption per 1000 VMAs becomes 48 pages, saving 2 pages compared to the 50 pages in the baseline: slabinfo after vm_area_struct changes: ... : ... vm_area_struct ... 192 42 2 : ... 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. [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/ Suren Baghdasaryan (4): mm: introduce vma_start_read_locked{_nested} helpers mm: move per-vma lock into vm_area_struct mm: replace rw_semaphore with atomic_t in vma_lock mm: move lesser used vma_area_struct members into the last cacheline include/linux/mm.h | 163 +++++++++++++++++++++++++++++++++++--- include/linux/mm_types.h | 59 +++++++++----- include/linux/mmap_lock.h | 3 + kernel/fork.c | 50 ++---------- mm/init-mm.c | 2 + mm/userfaultfd.c | 14 ++-- 6 files changed, 205 insertions(+), 86 deletions(-) base-commit: 931086f2a88086319afb57cd3925607e8cda0a9f -- 2.47.0.277.g8800431eea-goog