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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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 893FE1C0016 X-Stat-Signature: xszcfkb1rdnkfkp5sfbxp3uh3rfw8pme X-HE-Tag: 1730077716-288968 X-HE-Meta: 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 ybtDvcd7 NLaBJtoK2C/LD4VC/Eh1LyHRoIYQCARFrjLdEGoYeegvbMc8fKgccRw7MerKwPr1QPz55adlayeL5xwP7Ea/xbWxvBwZI7G5c2o8L0DEz+bx5wknQweDFsTOwcx4oArJT0WcJgcPKVVywawLSC+qCcDeF7a8cOpeb7aWHqJ7/5yI1Nv3n6vrIKozdc7gxTPfTBeFH9pVNMMm6xJTQ4sl0igzcQOT2XKYI88vwtsafBHQCuCTCg9YrmqLFnkOA4Zg5CLd0jEMtvdS/cNnT7PDa52fkoD52lOlG071Baf3qo5kW9Kk3djv0YPF+V/jb0oVeccPMydaayVmj3QbC+mdPHdrB+T4WXRVn2G77yG5slDX9oncV+B6bXy+vGd1fauVKA+RXJWhgIQLqGObQtDCoBQaQGU07R17RDkYxcZpPDaJ6s4k= 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 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) ============================= 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). Reviewed-by: Oleg Nesterov Suggested-by: Matthew Wilcox Suggested-by: Peter Zijlstra Signed-off-by: Andrii Nakryiko --- 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, 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; + loff_t offset; + unsigned int seq; + + guard(rcu)(); + + if (!mmap_lock_speculation_begin(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; + + offset = (loff_t)(vma->vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vma->vm_start); + uprobe = 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(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) { -- 2.43.5