From patchwork Thu Oct 10 20:56:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13831108 X-Patchwork-Delegate: bpf@iogearbox.net 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 AE7BA1E7C0D; Thu, 10 Oct 2024 20:57:00 +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=1728593820; cv=none; b=e6NvkEgXsY67T1mc9cM9h1Df+umjz1hdtggjl4PnQ70vTZPQuci0CP89sRetJxghzjNiHAosAoo9tJMEsm0PQ7FdcaiAXlHfwIHnpDB8PteM/npkUy1/tKOuvpXaA8lebsDhWzfkMG6JfqYia0wVTDjWdC4JWe6RydCwxQb4pLs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728593820; c=relaxed/simple; bh=HJW3q0theOLZJq7cr7mtCh0i3gb8IviMxWPJ1EUCK8Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=guNOyMcTrzcmdUStIPtmSuMZVU2hL0FCqOyMoIi78N4IQ9Ly80hw/O+W9Rn+HFzqVEP8G/Sp6ho4oVnnJuilvFTa3jqWr3vXzrghcMrrMgpU6yMPfpB8tVYIrletc2Aq/6VN9HTkZFFZTpJsS/e7xhnd/hVJ1hZIQHTDUbQl25s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M9r9qtsY; 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="M9r9qtsY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A9CDC4CEC5; Thu, 10 Oct 2024 20:57:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728593820; bh=HJW3q0theOLZJq7cr7mtCh0i3gb8IviMxWPJ1EUCK8Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M9r9qtsYZGd4X6+5xoplvdRL+ZFYzemjolVpIJwvK0szlb1y4gDtezvN8agSMJscW l4n9x4peZxFi5llEIv76G3TpR+pfmzHPzF2NSoaw2YIhGup95xfoeAm4oRZCF7ayw5 bbGSHUhxT8S9BdKGdGHM4xEO+L/XOQx4hrEnt4f1tip4yJVtIWocycxX5JlRZlQtY/ Jq4d4xgAK681mlSZf1Ska7NNLb7oxoBj4XXqlR1yGxHQs2lnLVsIAqcg9xwLWO8jBt Ii17mcAKVvPskH8m79ilR+9AuuycUxN0LXsNDSe98+NQxOZIBxERYE+M6SLXHueeUD P+CEOcJbWed1g== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, linux-mm@kvack.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, akpm@linux-foundation.org, 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, Andrii Nakryiko Subject: [PATCH v3 tip/perf/core 4/4] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Date: Thu, 10 Oct 2024 13:56:44 -0700 Message-ID: <20241010205644.3831427-5-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241010205644.3831427-1-andrii@kernel.org> References: <20241010205644.3831427-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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_{start,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) ============================= uprobe-nop ( 1 cpus): 3.384 ± 0.004M/s ( 3.384M/s/cpu) uprobe-nop ( 2 cpus): 5.456 ± 0.005M/s ( 2.728M/s/cpu) uprobe-nop ( 3 cpus): 7.863 ± 0.015M/s ( 2.621M/s/cpu) uprobe-nop ( 4 cpus): 9.442 ± 0.008M/s ( 2.360M/s/cpu) uprobe-nop ( 5 cpus): 11.036 ± 0.013M/s ( 2.207M/s/cpu) uprobe-nop ( 6 cpus): 10.884 ± 0.019M/s ( 1.814M/s/cpu) uprobe-nop ( 7 cpus): 7.897 ± 0.145M/s ( 1.128M/s/cpu) uprobe-nop ( 8 cpus): 10.021 ± 0.128M/s ( 1.253M/s/cpu) uprobe-nop (10 cpus): 9.932 ± 0.170M/s ( 0.993M/s/cpu) uprobe-nop (12 cpus): 8.369 ± 0.056M/s ( 0.697M/s/cpu) uprobe-nop (14 cpus): 8.678 ± 0.017M/s ( 0.620M/s/cpu) uprobe-nop (16 cpus): 7.392 ± 0.003M/s ( 0.462M/s/cpu) uprobe-nop (24 cpus): 5.326 ± 0.178M/s ( 0.222M/s/cpu) uprobe-nop (32 cpus): 5.426 ± 0.059M/s ( 0.170M/s/cpu) uprobe-nop (40 cpus): 5.262 ± 0.070M/s ( 0.132M/s/cpu) uprobe-nop (48 cpus): 6.121 ± 0.010M/s ( 0.128M/s/cpu) uprobe-nop (56 cpus): 6.252 ± 0.035M/s ( 0.112M/s/cpu) uprobe-nop (64 cpus): 7.644 ± 0.023M/s ( 0.119M/s/cpu) uprobe-nop (72 cpus): 7.781 ± 0.001M/s ( 0.108M/s/cpu) uprobe-nop (80 cpus): 8.992 ± 0.048M/s ( 0.112M/s/cpu) AFTER ===== uprobe-nop ( 1 cpus): 3.534 ± 0.033M/s ( 3.534M/s/cpu) uprobe-nop ( 2 cpus): 6.701 ± 0.007M/s ( 3.351M/s/cpu) uprobe-nop ( 3 cpus): 10.031 ± 0.007M/s ( 3.344M/s/cpu) uprobe-nop ( 4 cpus): 13.003 ± 0.012M/s ( 3.251M/s/cpu) uprobe-nop ( 5 cpus): 16.274 ± 0.006M/s ( 3.255M/s/cpu) uprobe-nop ( 6 cpus): 19.563 ± 0.024M/s ( 3.261M/s/cpu) uprobe-nop ( 7 cpus): 22.696 ± 0.054M/s ( 3.242M/s/cpu) uprobe-nop ( 8 cpus): 24.534 ± 0.010M/s ( 3.067M/s/cpu) uprobe-nop (10 cpus): 30.475 ± 0.117M/s ( 3.047M/s/cpu) uprobe-nop (12 cpus): 33.371 ± 0.017M/s ( 2.781M/s/cpu) uprobe-nop (14 cpus): 38.864 ± 0.004M/s ( 2.776M/s/cpu) uprobe-nop (16 cpus): 41.476 ± 0.020M/s ( 2.592M/s/cpu) uprobe-nop (24 cpus): 64.696 ± 0.021M/s ( 2.696M/s/cpu) uprobe-nop (32 cpus): 85.054 ± 0.027M/s ( 2.658M/s/cpu) uprobe-nop (40 cpus): 101.979 ± 0.032M/s ( 2.549M/s/cpu) uprobe-nop (48 cpus): 110.518 ± 0.056M/s ( 2.302M/s/cpu) uprobe-nop (56 cpus): 117.737 ± 0.020M/s ( 2.102M/s/cpu) uprobe-nop (64 cpus): 124.613 ± 0.079M/s ( 1.947M/s/cpu) uprobe-nop (72 cpus): 133.239 ± 0.032M/s ( 1.851M/s/cpu) uprobe-nop (80 cpus): 142.037 ± 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). Suggested-by: Matthew Wilcox Signed-off-by: Andrii Nakryiko Reviewed-by: Oleg Nesterov --- kernel/events/uprobes.c | 50 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index fa1024aad6c4..9dc6e78975c9 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2047,6 +2047,52 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr) return is_trap_insn(&opcode); } +static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vaddr) +{ + struct mm_struct *mm = current->mm; + struct uprobe *uprobe = NULL; + struct vm_area_struct *vma; + struct file *vm_file; + struct inode *vm_inode; + unsigned long vm_pgoff, vm_start; + loff_t offset; + long seq; + + guard(rcu)(); + + if (!mmap_lock_speculation_start(mm, &seq)) + return NULL; + + vma = 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 = READ_ONCE(vma->vm_file); + if (!vm_file) + return NULL; + + vm_pgoff = data_race(vma->vm_pgoff); + vm_start = data_race(vma->vm_start); + vm_inode = data_race(vm_file->f_inode); + + offset = (loff_t)(vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vm_start); + uprobe = find_uprobe_rcu(vm_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) { @@ -2054,6 +2100,10 @@ static struct uprobe *find_active_uprobe_rcu(unsigned long bp_vaddr, int *is_swb struct uprobe *uprobe = NULL; struct vm_area_struct *vma; + uprobe = find_active_uprobe_speculative(bp_vaddr); + if (uprobe) + return uprobe; + mmap_read_lock(mm); vma = vma_lookup(mm, bp_vaddr); if (vma) {