From nobody Mon Nov 25 12:45:23 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C700814D43D; Mon, 28 Oct 2024 01:09:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077749; cv=none; b=YhNUQ92WVsN5GCuKyMlz6xBxLy8a3uquaByT6pDw4qkP+pOcaYyvLoTuuKEO/7Ab2UlD17bXMGIZMeBo4ZRtHLQHOdbL/jmaRgrO3AJyjx3Ns0sMxtgKzMBpP37rRG91TV+Rzpvpp2bMkhEeVVCLZZbZ5pkQRmK/Ty9mOOTQNbo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077749; c=relaxed/simple; bh=Ribok69L0V+IQIfX1LKAa+j7slCTXJ/a5HygjFWCqNY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RxsO92yJ4Z8j2ZRVV6mfA0Iy/+6x0Rtvys/L2b21YCewEwIE2aIl6XPewj7oKAgFU+44iDnr8xm3JcDPludSOtzFHRGwpOZpeQmo3S1mgVGBskx9Xa7pA9x1PFuLhj5IMVxghtrXadKd2lE0rYvhEd42ufeJ523+tkZI+MKGWLY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XcEsDuxZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XcEsDuxZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65703C4CEE5; Mon, 28 Oct 2024 01:09:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730077749; bh=Ribok69L0V+IQIfX1LKAa+j7slCTXJ/a5HygjFWCqNY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XcEsDuxZ44cpUaR4KUbORo/ERRrafxKAF05h7Dd+n1ohShoR33iYzss2xVzkX9bZy NUA2c2/P93p+1NY9BMPbz4ZhkGNAColwIYcLIkLlh2xb7UNFCr/2OVBIwND0TfPClO beYu28enquoY3AqAvW6Rn0Hh1VpYSsaOhhkqDSzC3pNPmq+ARjE5S+TFvAdIRba7vC B251sDrDieSzrwoxJpURaYek9EDwPpQG1pvuqNwhl+W23/1EpA/uFDnIxtKnlI9F/A FmYTcm7H7O71F77iLvdRJxipSDNTwtQR1UO+1v/V0OA1iqT0qzRg8WsMBTP86OkiSe E2A9BGrGM6ZnA== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, arnd@arndb.de, richard.weiyang@gmail.com, zhangpeng.00@bytedance.com, linmiaohe@huawei.com, viro@zeniv.linux.org.uk, hca@linux.ibm.com, Andrii Nakryiko Subject: [PATCH v4 tip/perf/core 1/4] mm: Convert mm_lock_seq to a proper seqcount Date: Sun, 27 Oct 2024 18:08:15 -0700 Message-ID: <20241028010818.2487581-2-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241028010818.2487581-1-andrii@kernel.org> References: <20241028010818.2487581-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Suren Baghdasaryan Convert mm_lock_seq to be seqcount_t and change all mmap_write_lock variants to increment it, in-line with the usual seqcount usage pattern. This lets us check whether the mmap_lock is write-locked by checking mm_lock_seq.sequence counter (odd=3Dlocked, even=3Dunlocked). This will be used when implementing mmap_lock speculation functions. As a result vm_lock_seq is also change to be unsigned to match the type of mm_lock_seq.sequence. Suggested-by: Peter Zijlstra Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrii Nakryiko Acked-by: Vlastimil Babka --- include/linux/mm.h | 12 +++---- include/linux/mm_types.h | 7 ++-- include/linux/mmap_lock.h | 58 +++++++++++++++++++++----------- kernel/fork.c | 5 +-- mm/init-mm.c | 2 +- tools/testing/vma/vma.c | 4 +-- tools/testing/vma/vma_internal.h | 4 +-- 7 files changed, 56 insertions(+), 36 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index ecf63d2b0582..94b537088142 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -698,7 +698,7 @@ static inline bool vma_start_read(struct vm_area_struct= *vma) * we don't rely on for anything - the mm_lock_seq read against which we * need ordering is below. */ - if (READ_ONCE(vma->vm_lock_seq) =3D=3D READ_ONCE(vma->vm_mm->mm_lock_seq)) + if (READ_ONCE(vma->vm_lock_seq) =3D=3D READ_ONCE(vma->vm_mm->mm_lock_seq.= sequence)) return false; =20 if (unlikely(down_read_trylock(&vma->vm_lock->lock) =3D=3D 0)) @@ -715,7 +715,7 @@ static inline bool vma_start_read(struct vm_area_struct= *vma) * after it has been unlocked. * This pairs with RELEASE semantics in vma_end_write_all(). */ - if (unlikely(vma->vm_lock_seq =3D=3D smp_load_acquire(&vma->vm_mm->mm_loc= k_seq))) { + if (unlikely(vma->vm_lock_seq =3D=3D raw_read_seqcount(&vma->vm_mm->mm_lo= ck_seq))) { up_read(&vma->vm_lock->lock); return false; } @@ -730,7 +730,7 @@ static inline void vma_end_read(struct vm_area_struct *= vma) } =20 /* WARNING! Can only be used if mmap_lock is expected to be write-locked */ -static bool __is_vma_write_locked(struct vm_area_struct *vma, int *mm_lock= _seq) +static bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int= *mm_lock_seq) { mmap_assert_write_locked(vma->vm_mm); =20 @@ -738,7 +738,7 @@ static bool __is_vma_write_locked(struct vm_area_struct= *vma, int *mm_lock_seq) * current task is holding mmap_write_lock, both vma->vm_lock_seq and * mm->mm_lock_seq can't be concurrently modified. */ - *mm_lock_seq =3D vma->vm_mm->mm_lock_seq; + *mm_lock_seq =3D vma->vm_mm->mm_lock_seq.sequence; return (vma->vm_lock_seq =3D=3D *mm_lock_seq); } =20 @@ -749,7 +749,7 @@ static bool __is_vma_write_locked(struct vm_area_struct= *vma, int *mm_lock_seq) */ static inline void vma_start_write(struct vm_area_struct *vma) { - int mm_lock_seq; + unsigned int mm_lock_seq; =20 if (__is_vma_write_locked(vma, &mm_lock_seq)) return; @@ -767,7 +767,7 @@ static inline void vma_start_write(struct vm_area_struc= t *vma) =20 static inline void vma_assert_write_locked(struct vm_area_struct *vma) { - int mm_lock_seq; + unsigned int mm_lock_seq; =20 VM_BUG_ON_VMA(!__is_vma_write_locked(vma, &mm_lock_seq), vma); } diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 6e3bdf8e38bc..76e0cdc0462b 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -715,7 +715,7 @@ struct vm_area_struct { * counter reuse can only lead to occasional unnecessary use of the * slowpath. */ - int vm_lock_seq; + unsigned int vm_lock_seq; /* Unstable RCU readers are allowed to read this. */ struct vma_lock *vm_lock; #endif @@ -887,6 +887,9 @@ struct mm_struct { * Roughly speaking, incrementing the sequence number is * equivalent to releasing locks on VMAs; reading the sequence * number can be part of taking a read lock on a VMA. + * Incremented every time mmap_lock is write-locked/unlocked. + * Initialized to 0, therefore odd values indicate mmap_lock + * is write-locked and even values that it's released. * * Can be modified under write mmap_lock using RELEASE * semantics. @@ -895,7 +898,7 @@ struct mm_struct { * Can be read with ACQUIRE semantics if not holding write * mmap_lock. */ - int mm_lock_seq; + seqcount_t mm_lock_seq; #endif =20 =20 diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index de9dc20b01ba..6b3272686860 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -71,39 +71,38 @@ static inline void mmap_assert_write_locked(const struc= t mm_struct *mm) } =20 #ifdef CONFIG_PER_VMA_LOCK -/* - * Drop all currently-held per-VMA locks. - * This is called from the mmap_lock implementation directly before releas= ing - * a write-locked mmap_lock (or downgrading it to read-locked). - * This should normally NOT be called manually from other places. - * If you want to call this manually anyway, keep in mind that this will r= elease - * *all* VMA write locks, including ones from further up the stack. - */ -static inline void vma_end_write_all(struct mm_struct *mm) +static inline void mm_lock_seqcount_init(struct mm_struct *mm) { - mmap_assert_write_locked(mm); - /* - * Nobody can concurrently modify mm->mm_lock_seq due to exclusive - * mmap_lock being held. - * We need RELEASE semantics here to ensure that preceding stores into - * the VMA take effect before we unlock it with this store. - * Pairs with ACQUIRE semantics in vma_start_read(). - */ - smp_store_release(&mm->mm_lock_seq, mm->mm_lock_seq + 1); + seqcount_init(&mm->mm_lock_seq); +} + +static inline void mm_lock_seqcount_begin(struct mm_struct *mm) +{ + do_raw_write_seqcount_begin(&mm->mm_lock_seq); +} + +static inline void mm_lock_seqcount_end(struct mm_struct *mm) +{ + do_raw_write_seqcount_end(&mm->mm_lock_seq); } + #else -static inline void vma_end_write_all(struct mm_struct *mm) {} +static inline void mm_lock_seqcount_init(struct mm_struct *mm) {} +static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {} +static inline void mm_lock_seqcount_end(struct mm_struct *mm) {} #endif =20 static inline void mmap_init_lock(struct mm_struct *mm) { init_rwsem(&mm->mmap_lock); + mm_lock_seqcount_init(mm); } =20 static inline void mmap_write_lock(struct mm_struct *mm) { __mmap_lock_trace_start_locking(mm, true); down_write(&mm->mmap_lock); + mm_lock_seqcount_begin(mm); __mmap_lock_trace_acquire_returned(mm, true, true); } =20 @@ -111,6 +110,7 @@ static inline void mmap_write_lock_nested(struct mm_str= uct *mm, int subclass) { __mmap_lock_trace_start_locking(mm, true); down_write_nested(&mm->mmap_lock, subclass); + mm_lock_seqcount_begin(mm); __mmap_lock_trace_acquire_returned(mm, true, true); } =20 @@ -120,10 +120,30 @@ static inline int mmap_write_lock_killable(struct mm_= struct *mm) =20 __mmap_lock_trace_start_locking(mm, true); ret =3D down_write_killable(&mm->mmap_lock); + if (!ret) + mm_lock_seqcount_begin(mm); __mmap_lock_trace_acquire_returned(mm, true, ret =3D=3D 0); return ret; } =20 +/* + * Drop all currently-held per-VMA locks. + * This is called from the mmap_lock implementation directly before releas= ing + * a write-locked mmap_lock (or downgrading it to read-locked). + * This should normally NOT be called manually from other places. + * If you want to call this manually anyway, keep in mind that this will r= elease + * *all* VMA write locks, including ones from further up the stack. + */ +static inline void vma_end_write_all(struct mm_struct *mm) +{ + mmap_assert_write_locked(mm); + /* + * Nobody can concurrently modify mm->mm_lock_seq due to exclusive + * mmap_lock being held. + */ + mm_lock_seqcount_end(mm); +} + static inline void mmap_write_unlock(struct mm_struct *mm) { __mmap_lock_trace_released(mm, true); diff --git a/kernel/fork.c b/kernel/fork.c index 89ceb4a68af2..55c4088543dc 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -448,7 +448,7 @@ static bool vma_lock_alloc(struct vm_area_struct *vma) return false; =20 init_rwsem(&vma->vm_lock->lock); - vma->vm_lock_seq =3D -1; + vma->vm_lock_seq =3D UINT_MAX; =20 return true; } @@ -1261,9 +1261,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm= , struct task_struct *p, seqcount_init(&mm->write_protect_seq); mmap_init_lock(mm); INIT_LIST_HEAD(&mm->mmlist); -#ifdef CONFIG_PER_VMA_LOCK - mm->mm_lock_seq =3D 0; -#endif mm_pgtables_bytes_init(mm); mm->map_count =3D 0; mm->locked_vm =3D 0; diff --git a/mm/init-mm.c b/mm/init-mm.c index 24c809379274..6af3ad675930 100644 --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -40,7 +40,7 @@ struct mm_struct init_mm =3D { .arg_lock =3D __SPIN_LOCK_UNLOCKED(init_mm.arg_lock), .mmlist =3D LIST_HEAD_INIT(init_mm.mmlist), #ifdef CONFIG_PER_VMA_LOCK - .mm_lock_seq =3D 0, + .mm_lock_seq =3D SEQCNT_ZERO(init_mm.mm_lock_seq), #endif .user_ns =3D &init_user_ns, .cpu_bitmap =3D CPU_BITS_NONE, diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c index c53f220eb6cc..bcdf831dfe3e 100644 --- a/tools/testing/vma/vma.c +++ b/tools/testing/vma/vma.c @@ -87,7 +87,7 @@ static struct vm_area_struct *alloc_and_link_vma(struct m= m_struct *mm, * begun. Linking to the tree will have caused this to be incremented, * which means we will get a false positive otherwise. */ - vma->vm_lock_seq =3D -1; + vma->vm_lock_seq =3D UINT_MAX; =20 return vma; } @@ -212,7 +212,7 @@ static bool vma_write_started(struct vm_area_struct *vm= a) int seq =3D vma->vm_lock_seq; =20 /* We reset after each check. */ - vma->vm_lock_seq =3D -1; + vma->vm_lock_seq =3D UINT_MAX; =20 /* The vma_start_write() stub simply increments this value. */ return seq > -1; diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_inter= nal.h index c5b9da034511..4007ec580f85 100644 --- a/tools/testing/vma/vma_internal.h +++ b/tools/testing/vma/vma_internal.h @@ -231,7 +231,7 @@ struct vm_area_struct { * counter reuse can only lead to occasional unnecessary use of the * slowpath. */ - int vm_lock_seq; + unsigned int vm_lock_seq; struct vma_lock *vm_lock; #endif =20 @@ -406,7 +406,7 @@ static inline bool vma_lock_alloc(struct vm_area_struct= *vma) return false; =20 init_rwsem(&vma->vm_lock->lock); - vma->vm_lock_seq =3D -1; + vma->vm_lock_seq =3D UINT_MAX; =20 return true; } --=20 2.43.5 From nobody Mon Nov 25 12:45:23 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E89FB13774D; Mon, 28 Oct 2024 01:09:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077753; cv=none; b=bvucaNJmB2DFwThLuZCbHeF9IsFDiGN9QCNR5wdyd0AvQblTWGN908XS+/sQ+gHDR4gSSvbe6XtpndMuC/dJmSb1AWv9Eer6wzXlSUtRWHIQiAPfw1yXJJVqY348Wab3KqSstGbEINxnHMVNv9ycl8UkwvXJal38aUp2f3akOCU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077753; c=relaxed/simple; bh=hDtDfS8JqT/fLQMiv3m8WVup/RU6yhW70oJ6haQb60E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dfR8wtMidNFkCXcS1vvuUYd/FzfTR2JZ6IwjEmy2CV0/j36PE/lSMBQMzsrvFPQwW8ncsH/Fp0yrLtLijchYZBaqdwBGi9krAApU+x33lHlKukdK1TJphBhDKqqaTiyPZtS2BE/26KnbHzCuZfPRE5Lc1WpU4gKQup16NGNy8B4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R3D7Ov04; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R3D7Ov04" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E76EC4CEE5; Mon, 28 Oct 2024 01:09:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730077752; bh=hDtDfS8JqT/fLQMiv3m8WVup/RU6yhW70oJ6haQb60E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R3D7Ov04DpaTyYJl+4SfPWoXLMI5EldjfTRT6VKHmSxekQRYCT+7e+vroidwAIM/y c9UyoWB0yeHAQH9wTW7L78nHqBKgCt8ub4xAaiUUNjh1wTF2ra5CO9zN6Y1+ZM9WXu XyH8q6zDh3Q2i8O3Z0GTJGneeTd+hwvD+2koWe7Tt+V5W6IjIOahBvgr/w8QyRKLZX zh3XZeFvlXwBaoY/ZbL/16DKFuEy1Pqn1S42YcpEXwRg9wU7Db45SReuz3aoSXoDcX pYqPLyrc4kC79COC4fnmbguofXh/ZDGrmKdLWt0rsIyDhYk4VXtGueWWod/9Y+SFIn 07MKzAQ58jXyA== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, arnd@arndb.de, richard.weiyang@gmail.com, zhangpeng.00@bytedance.com, linmiaohe@huawei.com, viro@zeniv.linux.org.uk, hca@linux.ibm.com, Andrii Nakryiko Subject: [PATCH v4 tip/perf/core 2/4] mm: Introduce mmap_lock_speculation_{begin|end} Date: Sun, 27 Oct 2024 18:08:16 -0700 Message-ID: <20241028010818.2487581-3-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241028010818.2487581-1-andrii@kernel.org> References: <20241028010818.2487581-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Suren Baghdasaryan Add helper functions to speculatively perform operations without read-locking mmap_lock, expecting that mmap_lock will not be write-locked and mm is not modified from under us. Suggested-by: Peter Zijlstra Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrii Nakryiko Acked-by: Vlastimil Babka --- include/linux/mmap_lock.h | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 6b3272686860..58dde2e35f7e 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -71,6 +71,7 @@ static inline void mmap_assert_write_locked(const struct = mm_struct *mm) } =20 #ifdef CONFIG_PER_VMA_LOCK + static inline void mm_lock_seqcount_init(struct mm_struct *mm) { seqcount_init(&mm->mm_lock_seq); @@ -86,11 +87,35 @@ static inline void mm_lock_seqcount_end(struct mm_struc= t *mm) do_raw_write_seqcount_end(&mm->mm_lock_seq); } =20 -#else +static inline bool mmap_lock_speculation_begin(struct mm_struct *mm, unsig= ned int *seq) +{ + *seq =3D raw_read_seqcount(&mm->mm_lock_seq); + /* Allow speculation if mmap_lock is not write-locked */ + return (*seq & 1) =3D=3D 0; +} + +static inline bool mmap_lock_speculation_end(struct mm_struct *mm, unsigne= d int seq) +{ + return !do_read_seqcount_retry(&mm->mm_lock_seq, seq); +} + +#else /* CONFIG_PER_VMA_LOCK */ + static inline void mm_lock_seqcount_init(struct mm_struct *mm) {} static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {} static inline void mm_lock_seqcount_end(struct mm_struct *mm) {} -#endif + +static inline bool mmap_lock_speculation_begin(struct mm_struct *mm, unsig= ned int *seq) +{ + return false; +} + +static inline bool mmap_lock_speculation_end(struct mm_struct *mm, unsigne= d int seq) +{ + return false; +} + +#endif /* CONFIG_PER_VMA_LOCK */ =20 static inline void mmap_init_lock(struct mm_struct *mm) { --=20 2.43.5 From nobody Mon Nov 25 12:45:23 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3A96813774D; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hHZTZEzL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B52B2C4CEC3; Mon, 28 Oct 2024 01:09:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730077755; bh=d0t2KdzFB54YqijRSkN8zgCUkKArImLR1/o5M57T+Y4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hHZTZEzLr1iL3FHbaDuT4QMbEbbJCKfdJHak1Cphw3Io7OVy4N+9xviZFpn66aI1f PlJOkge1nFNeUdTsUnrOMPN1hqSeV1o0gMm9Lg/U2BhrunABIRUiRijxF0F2+CkU8d v58avLtFpLU/wQJTBPSWS4XGJpq96/WS8igjo7MUUUodF4yAQ3kroN4bJHsKngkHlT l8xJpHr70NPY6NK78bXQv05YYUiquo6oYCTtSTdJKylBEBOTHst9WNjrRy8s45NIDO bgUj7V6k42jCxv/1X9EWh7uooH0Cih40WwIP7W2TzNwQMR6cvih5Yu9jll42E3zSyv TwSiGKYcMRJ4g== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, arnd@arndb.de, richard.weiyang@gmail.com, zhangpeng.00@bytedance.com, linmiaohe@huawei.com, viro@zeniv.linux.org.uk, hca@linux.ibm.com, Andrii Nakryiko Subject: [PATCH v4 tip/perf/core 3/4] uprobes: simplify find_active_uprobe_rcu() VMA checks Date: Sun, 27 Oct 2024 18:08:17 -0700 Message-ID: <20241028010818.2487581-4-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241028010818.2487581-1-andrii@kernel.org> References: <20241028010818.2487581-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" At the point where find_active_uprobe_rcu() is used we know that VMA in question has triggered software breakpoint, so we don't need to validate vma->vm_flags. Keep only vma->vm_file NULL check. Acked-by: Oleg Nesterov Suggested-by: Oleg Nesterov Signed-off-by: Andrii Nakryiko Reviewed-by: Masami Hiramatsu (Google) --- kernel/events/uprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 4ef4b51776eb..290c445768fa 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2084,7 +2084,7 @@ static struct uprobe *find_active_uprobe_rcu(unsigned= long bp_vaddr, int *is_swb mmap_read_lock(mm); vma =3D vma_lookup(mm, bp_vaddr); if (vma) { - if (valid_vma(vma, false)) { + if (vma->vm_file) { struct inode *inode =3D file_inode(vma->vm_file); loff_t offset =3D vaddr_to_offset(vma, bp_vaddr); =20 --=20 2.43.5 From nobody Mon Nov 25 12:45:23 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8F6ED13774D; Mon, 28 Oct 2024 01:09:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077761; cv=none; b=fVnlMBVLIPKxrmYLRP+EHF+FWLUlY3VLqc60+NVt1JLFTNhbDPFOWgjo0KbPKqgdzc/ZJBWOvbkBCYTprGfN5eqiCqfF8a/kmi7/JKa3ySnU6dlx+UaXE7loO8k0i5CfJPwYwREV3OF+r+GM2jGaAEpGcRQ6HHtShAGrRFv6o7A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730077761; c=relaxed/simple; bh=ZPNLuHrFYNEi/W8csmpQZbPF0DFPLMywDg12QmBzVuo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=goTFoqBJ4VMGgAEXf7NXXq4DndxGRtvtbgqFkW+fjW+MJMavKS1Na1pT5t+wfzv1eD8MX3Tg46DmI4o8E1cKFMlxZ63gpxiv7H3JtXkNkcGZSFq5pYJU0pyiToShIsNO86uldc+wlsoiEhFm77LY33UxUDPD/GiDBLbyjvtCaQY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=C+buo1Is; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="C+buo1Is" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBD65C4CEC3; Mon, 28 Oct 2024 01:09:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730077759; bh=ZPNLuHrFYNEi/W8csmpQZbPF0DFPLMywDg12QmBzVuo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=C+buo1IsmnmycbNipf2rWZz2vBDbL5OVKi0LpMB8qqcKP41Owf6Z+9wSLvCIBOUrK pcTMZVwiVv4+puvahD9XAPMXxnzik04MGXvx8kxcZPLvlLmNL+UxJgt7ewpybKjvyL ePYifjLrGv2XPtXutiMdOB67aGoI0K7p53B59Pc0ZHzIzP4LN8KI7zxZfkjF9wa4J3 nbQVp3MCBiBBnht22dd66CzJzTkuJ2ZTvKWw+rt+E8+1mQ1yTvrYC9I/Rs34qXHn63 5OFjAIFOvUgmZl5mv8o7MDqV80mCtIkB9c+TfQaYtiWsJg4fIvedudx/XPNZSQ3kVF SuBgNsD3uVvyQ== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, peterz@infradead.org Cc: oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, arnd@arndb.de, richard.weiyang@gmail.com, zhangpeng.00@bytedance.com, linmiaohe@huawei.com, viro@zeniv.linux.org.uk, hca@linux.ibm.com, Andrii Nakryiko Subject: [PATCH v4 tip/perf/core 4/4] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Date: Sun, 27 Oct 2024 18:08:18 -0700 Message-ID: <20241028010818.2487581-5-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241028010818.2487581-1-andrii@kernel.org> References: <20241028010818.2487581-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Given filp_cachep is marked SLAB_TYPESAFE_BY_RCU (and FMODE_BACKING files, a special case, now goes through RCU-delated freeing), we can safely access vma->vm_file->f_inode field locklessly under just rcu_read_lock() protection, which enables looking up uprobe from uprobes_tree completely locklessly and speculatively without the need to acquire mmap_lock for reads. In most cases, anyway, assuming that there are no parallel mm and/or VMA modifications. The underlying struct file's memory won't go away from under us (even if struct file can be reused in the meantime). We rely on newly added mmap_lock_speculation_{begin,end}() helpers to validate that mm_struct stays intact for entire duration of this speculation. If not, we fall back to mmap_lock-protected lookup. The speculative logic is written in such a way that it will safely handle any garbage values that might be read from vma or file structs. Benchmarking results speak for themselves. BEFORE (latest tip/perf/core) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.384 =C2=B1 0.004M/s ( 3.384M/s/cpu) uprobe-nop ( 2 cpus): 5.456 =C2=B1 0.005M/s ( 2.728M/s/cpu) uprobe-nop ( 3 cpus): 7.863 =C2=B1 0.015M/s ( 2.621M/s/cpu) uprobe-nop ( 4 cpus): 9.442 =C2=B1 0.008M/s ( 2.360M/s/cpu) uprobe-nop ( 5 cpus): 11.036 =C2=B1 0.013M/s ( 2.207M/s/cpu) uprobe-nop ( 6 cpus): 10.884 =C2=B1 0.019M/s ( 1.814M/s/cpu) uprobe-nop ( 7 cpus): 7.897 =C2=B1 0.145M/s ( 1.128M/s/cpu) uprobe-nop ( 8 cpus): 10.021 =C2=B1 0.128M/s ( 1.253M/s/cpu) uprobe-nop (10 cpus): 9.932 =C2=B1 0.170M/s ( 0.993M/s/cpu) uprobe-nop (12 cpus): 8.369 =C2=B1 0.056M/s ( 0.697M/s/cpu) uprobe-nop (14 cpus): 8.678 =C2=B1 0.017M/s ( 0.620M/s/cpu) uprobe-nop (16 cpus): 7.392 =C2=B1 0.003M/s ( 0.462M/s/cpu) uprobe-nop (24 cpus): 5.326 =C2=B1 0.178M/s ( 0.222M/s/cpu) uprobe-nop (32 cpus): 5.426 =C2=B1 0.059M/s ( 0.170M/s/cpu) uprobe-nop (40 cpus): 5.262 =C2=B1 0.070M/s ( 0.132M/s/cpu) uprobe-nop (48 cpus): 6.121 =C2=B1 0.010M/s ( 0.128M/s/cpu) uprobe-nop (56 cpus): 6.252 =C2=B1 0.035M/s ( 0.112M/s/cpu) uprobe-nop (64 cpus): 7.644 =C2=B1 0.023M/s ( 0.119M/s/cpu) uprobe-nop (72 cpus): 7.781 =C2=B1 0.001M/s ( 0.108M/s/cpu) uprobe-nop (80 cpus): 8.992 =C2=B1 0.048M/s ( 0.112M/s/cpu) AFTER =3D=3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.534 =C2=B1 0.033M/s ( 3.534M/s/cpu) uprobe-nop ( 2 cpus): 6.701 =C2=B1 0.007M/s ( 3.351M/s/cpu) uprobe-nop ( 3 cpus): 10.031 =C2=B1 0.007M/s ( 3.344M/s/cpu) uprobe-nop ( 4 cpus): 13.003 =C2=B1 0.012M/s ( 3.251M/s/cpu) uprobe-nop ( 5 cpus): 16.274 =C2=B1 0.006M/s ( 3.255M/s/cpu) uprobe-nop ( 6 cpus): 19.563 =C2=B1 0.024M/s ( 3.261M/s/cpu) uprobe-nop ( 7 cpus): 22.696 =C2=B1 0.054M/s ( 3.242M/s/cpu) uprobe-nop ( 8 cpus): 24.534 =C2=B1 0.010M/s ( 3.067M/s/cpu) uprobe-nop (10 cpus): 30.475 =C2=B1 0.117M/s ( 3.047M/s/cpu) uprobe-nop (12 cpus): 33.371 =C2=B1 0.017M/s ( 2.781M/s/cpu) uprobe-nop (14 cpus): 38.864 =C2=B1 0.004M/s ( 2.776M/s/cpu) uprobe-nop (16 cpus): 41.476 =C2=B1 0.020M/s ( 2.592M/s/cpu) uprobe-nop (24 cpus): 64.696 =C2=B1 0.021M/s ( 2.696M/s/cpu) uprobe-nop (32 cpus): 85.054 =C2=B1 0.027M/s ( 2.658M/s/cpu) uprobe-nop (40 cpus): 101.979 =C2=B1 0.032M/s ( 2.549M/s/cpu) uprobe-nop (48 cpus): 110.518 =C2=B1 0.056M/s ( 2.302M/s/cpu) uprobe-nop (56 cpus): 117.737 =C2=B1 0.020M/s ( 2.102M/s/cpu) uprobe-nop (64 cpus): 124.613 =C2=B1 0.079M/s ( 1.947M/s/cpu) uprobe-nop (72 cpus): 133.239 =C2=B1 0.032M/s ( 1.851M/s/cpu) uprobe-nop (80 cpus): 142.037 =C2=B1 0.138M/s ( 1.775M/s/cpu) Previously total throughput was maxing out at 11mln/s, and gradually declining past 8 cores. With this change, it now keeps growing with each added CPU, reaching 142mln/s at 80 CPUs (this was measured on a 80-core Intel(R) Xeon(R) Gold 6138 CPU @ 2.00GHz). Reviewed-by: Oleg Nesterov Suggested-by: Matthew Wilcox Suggested-by: Peter Zijlstra Signed-off-by: Andrii Nakryiko Acked-by: Masami Hiramatsu (Google) --- kernel/events/uprobes.c | 45 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 290c445768fa..efcd62f7051d 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2074,6 +2074,47 @@ static int is_trap_at_addr(struct mm_struct *mm, uns= igned long vaddr) return is_trap_insn(&opcode); } =20 +static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vadd= r) +{ + struct mm_struct *mm =3D current->mm; + struct uprobe *uprobe =3D NULL; + struct vm_area_struct *vma; + struct file *vm_file; + loff_t offset; + unsigned int seq; + + guard(rcu)(); + + if (!mmap_lock_speculation_begin(mm, &seq)) + return NULL; + + vma =3D vma_lookup(mm, bp_vaddr); + if (!vma) + return NULL; + + /* + * vm_file memory can be reused for another instance of struct file, + * but can't be freed from under us, so it's safe to read fields from + * it, even if the values are some garbage values; ultimately + * find_uprobe_rcu() + mmap_lock_speculation_end() check will ensure + * that whatever we speculatively found is correct + */ + vm_file =3D READ_ONCE(vma->vm_file); + if (!vm_file) + return NULL; + + offset =3D (loff_t)(vma->vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vma->vm_st= art); + uprobe =3D find_uprobe_rcu(vm_file->f_inode, offset); + if (!uprobe) + return NULL; + + /* now double check that nothing about MM changed */ + if (!mmap_lock_speculation_end(mm, seq)) + return NULL; + + return uprobe; +} + /* assumes being inside RCU protected region */ static struct uprobe *find_active_uprobe_rcu(unsigned long bp_vaddr, int *= is_swbp) { @@ -2081,6 +2122,10 @@ static struct uprobe *find_active_uprobe_rcu(unsigne= d long bp_vaddr, int *is_swb struct uprobe *uprobe =3D NULL; struct vm_area_struct *vma; =20 + uprobe =3D find_active_uprobe_speculative(bp_vaddr); + if (uprobe) + return uprobe; + mmap_read_lock(mm); vma =3D vma_lookup(mm, bp_vaddr); if (vma) { --=20 2.43.5