From nobody Mon Nov 25 15:02:04 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