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Fri, 6 Sep 2024 05:12:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 073E6C4CEC6; Fri, 6 Sep 2024 05:12:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1725599542; bh=a4NkBvZonTqJ8yoj/hSxb9ICiGMU6QXUrxyQkC7Vl7w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QV5vPYv97/m9EPJuKGcj8XYI2CIWFnMfV9qyOikRm2O2gONtbgbefgY1QLUToUfoI JGeqHH2XYcPRFqsIWepREFHoU4xeN9TEd0AkFH+iIYtYK1Rg0Ex98g80m2ssNbkxqg yrm3OuQYfId7lYZ8+GRSXf/mkEbATfZTqBc6UjtN9oUPEhiAo9QJhq78lDyUL16DWA PToWOgAQgGVUwkfytLNTxnmkD/wfUD9grIspqyWdMdftMmXOy4ls4XEwfG3PV0BbYj /olCX9wwPbpeFpFV7bS/whMyssZ5/N/5sxen+31HVo7vSb9CS2IqwIUYWhIQ9Wjf1H 4DQab422ljrsg== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com Cc: 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, linux-mm@kvack.org, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, Andrii Nakryiko Subject: [PATCH 2/2] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Date: Thu, 5 Sep 2024 22:12:05 -0700 Message-ID: <20240906051205.530219-3-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20240906051205.530219-1-andrii@kernel.org> References: <20240906051205.530219-1-andrii@kernel.org> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Queue-Id: CDC9A180007 X-Rspamd-Server: rspam01 X-Stat-Signature: hh3fmcjibw4k9f9u845ntxwu69rbxjr3 X-HE-Tag: 1725599543-105591 X-HE-Meta: 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 OslCdJkH QGAuAP6InzorzWmlKWcXtgcd17dbm/uLjugukwrco4E2gCIye8w7Ap6xiW4QNru3VRipYveniWYi8/84DwxGbRJhlcWzn/XufMr9WnjgZHn//RL89KReQwgKPNLEH720BZOOw34y27oHYwzOAhbfgqbtm4bs7wl/8kPAGBrMgyGwE5YDnLf3QGqjoCshl4ZYgWAdG9bWSyMhmOuplZnfQBbjMfG11B9FESznhiRGmpHV5HCappgz8eAQ4i/d8Vbw8qUHCcdjNHGtSEkQLSZhDzSZcA4eNdSjDon0jRHHqOUmOo++hnXGGgc6+HDN9dm2eh1AY4lPZtYAduck= 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: Given filp_cachep is already marked SLAB_TYPESAFE_BY_RCU, 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, under the assumption 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 --- kernel/events/uprobes.c | 51 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index a2e6a57f79f2..b7e0baa83de1 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2081,6 +2081,53 @@ 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) +{ + const vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE; + struct mm_struct *mm = current->mm; + struct uprobe *uprobe; + struct vm_area_struct *vma; + struct file *vm_file; + struct inode *vm_inode; + unsigned long vm_pgoff, vm_start; + int seq; + loff_t offset; + + if (!mmap_lock_speculation_start(mm, &seq)) + return NULL; + + rcu_read_lock(); + + vma = vma_lookup(mm, bp_vaddr); + if (!vma) + goto bail; + + vm_file = data_race(vma->vm_file); + if (!vm_file || (vma->vm_flags & flags) != VM_MAYEXEC) + goto bail; + + vm_inode = data_race(vm_file->f_inode); + vm_pgoff = data_race(vma->vm_pgoff); + vm_start = data_race(vma->vm_start); + + offset = (loff_t)(vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vm_start); + uprobe = find_uprobe_rcu(vm_inode, offset); + if (!uprobe) + goto bail; + + /* now double check that nothing about MM changed */ + if (!mmap_lock_speculation_end(mm, seq)) + goto bail; + + rcu_read_unlock(); + + /* happy case, we speculated successfully */ + return uprobe; +bail: + rcu_read_unlock(); + return NULL; +} + /* assumes being inside RCU protected region */ static struct uprobe *find_active_uprobe_rcu(unsigned long bp_vaddr, int *is_swbp) { @@ -2088,6 +2135,10 @@ 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) {