From patchwork Tue Aug 13 04:29:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 13761229 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 D80F71CD16; Tue, 13 Aug 2024 04:29:40 +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=1723523380; cv=none; b=s4XF6FP7G32M1hWGYHgBf/i2LU4ULRCWun2o8qZhxRho4nTam2/lcBT0S1i5SMNuHSbXwsZFohYT1BBQa9caSCAapqdxyjabWq5qK69xZLf9uN4/HJKj1UBBvRLSWXNaZwa9xaZJ/xtYufDH+XpHNM5PDt9Gocv6WhYdhPYwMkA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723523380; c=relaxed/simple; bh=9iIC+w6MzgIDZ57yrgD+NVnkaNmR+cOiY2NRDqW/xEQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=SyWmWPdbnntKncILbUvaVNXu76VtS1EEb0Lt+yWNlZR7zxfxMRUfAgc6WcR0UbyNJo+/9wRXO6i/mDsyu/nbpjDSjxuaY1A72uOVtQdCeCU8mKChAql+e/OOGxyN/HXLL03mi+f14rzjHPU9EdSTzE2zM27a1Mwe5+aWQZZy0Nw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ehCVoOpa; 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="ehCVoOpa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 328A5C4AF09; Tue, 13 Aug 2024 04:29:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1723523380; bh=9iIC+w6MzgIDZ57yrgD+NVnkaNmR+cOiY2NRDqW/xEQ=; h=From:To:Cc:Subject:Date:From; b=ehCVoOpaBOtL09Y8PK0a45ryaSIO/AWEAzRlv+FbHh576LX8DZHeRCcYi2iDl1Rf1 4k65BCB+yZ+38KQuGKAlmYBvlZqH2Bhi9ys6MNKJe43tUhY+94g0AcQ/9UnrSg/Z1q iDTWadJtyUanw0FckDjrS8rujxpO4tJIBgc3knLvkD9HB1meugTotLISLx8/kRvOr7 VEYwI9DRq9J1L9OoA16BUZuX9SenPEdcDVIyG6iPenzQJtPsI8EAx3jV2N8FVDFakY EDMQLFe7cvERR9w5i1VYUSd488tyyfHQYSvUtw8xWEfAgIW5qIPKwxf2anrQfVp6oR pWjUez5IDX6ag== 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, Andrii Nakryiko Subject: [PATCH v3 00/13] uprobes: RCU-protected hot path optimizations Date: Mon, 12 Aug 2024 21:29:04 -0700 Message-ID: <20240813042917.506057-1-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 ( In addition to previously posted first 8 patches, I'm sending 5 more as an RFC for people to get the general gist of where this work heading and what uprobe performance is now achievable. I think first 8 patches are ready to be applied and I'd appreciate early feedback on the remaining 5 ones. Patches #9 and #10 implement SRCU-based refcounting avoidance for return_instance and single-stepped uprobes, and lockless SRCU expiration by timeout. Please look at hprobe_*() helpers for most of the details. Last three patches are implementing lockless VMA -> uprobe resolution logic by relying on a) SLAB_TYPESAFE_BY_RCU protection for files_cachep and b) on Suren's mm_lock_seq changes. Note benchmarking numbers in the last patch. The remainder of cover letter is written as applied to only first 8 patches. ) This patch set is heavily inspired by Peter Zijlstra's uprobe optimization patches ([0]) and continue that work, albeit trying to keep complexity to the minimum, and attepting to reuse existing primitives as much as possible. The goal here is to optimize obvious uprobe triggering hot path, while keeping the rest of locking mostly intact. I've added uprobe_unregister_sync() into the error handling code path inside uprobe_unregister(). This is due to recent refactorings from Oleg Nesterov ([1]), which necessitates this addition. Except for refcounting change patch (which I stongly believe is a good improvement we should do and forget about quasi-refcounting schema of uprobe->consumers list), the rest of the changes are similar to Peter's initial changes in [0]. Main differences would be: - no special RCU protection for mmap and fork handling, we just stick to refcounts there, as those are infrequent and not performance-sensitive code, while being complex and thus benefiting from proper locking; - the above means we don't need to do any custom SRCU additions to handle forking code path; - I handled UPROBE_HANDLER_REMOVE problem in handler_chain() differently, again, leveraging existing locking scheam; - I kept refcount usage for uretprobe and single-stepping uprobes, I plan to address that in a separate follow up patches. The plan is to avoid task_work, but I need to sit down and write and test the code. - finally, I dutifully was using SRCU throughout all the changes, and only last patch switches SRCU to RCU Tasks Trace and demonstrates significant performance and scalability gains from this. The changes in this patch set were tested using BPF selftests and using uprobe-stress ([2]) tool. One recent BPF selftest (uprobe_multi/consumers), only recently added by Jiri Olsa will need a single-line adjustment to the counting logic, but the patch itself is in bpf-next/master, so we'll have to address that once linux-trace or tip and bpf-next trees merge. I'll take care of that when this happens. Now, for the benchmarking results. I've used the following script (which utilizes BPF selftests-based bench tool). The CPU used was 80-core Intel Xeon Gold 6138 CPU @ 2.00GHz running kernel with production-like config. I minimized background noise by stopping any service I could identify and stop, so results are pretty stable and variability is pretty small, overall. Benchmark script: #!/bin/bash set -eufo pipefail for i in uprobe-nop uretprobe-nop; do for p in 1 2 4 8 16 32 64; do summary=$(sudo ./bench -w3 -d5 -p$p -a trig-$i | tail -n1) total=$(echo "$summary" | cut -d'(' -f1 | cut -d' ' -f3-) percpu=$(echo "$summary" | cut -d'(' -f2 | cut -d')' -f1 | cut -d'/' -f1) printf "%-15s (%2d cpus): %s (%s/s/cpu)\n" $i $p "$total" "$percpu" done echo done With all the lock-avoiding changes done in this patch set, we get a pretty decent improvement in performance and scalability of uprobes with number of CPUs, even though we are still nowhere near linear scalability. This is due to the remaining mmap_lock, which is currently taken to resolve interrupt address to inode+offset and then uprobe instance. And, of course, uretprobes still need similar RCU to avoid refcount in the hot path, which will be addressed in the follow up patches. (Again, note, I left the benchmark numbers with lockless RB-tree patches in.) BASELINE (on top of Oleg's clean up patches) ============================================ uprobe-nop ( 1 cpus): 3.032 ± 0.023M/s ( 3.032M/s/cpu) uprobe-nop ( 2 cpus): 3.452 ± 0.005M/s ( 1.726M/s/cpu) uprobe-nop ( 4 cpus): 3.663 ± 0.005M/s ( 0.916M/s/cpu) uprobe-nop ( 8 cpus): 3.718 ± 0.038M/s ( 0.465M/s/cpu) uprobe-nop (16 cpus): 3.344 ± 0.008M/s ( 0.209M/s/cpu) uprobe-nop (32 cpus): 2.288 ± 0.021M/s ( 0.071M/s/cpu) uprobe-nop (64 cpus): 3.205 ± 0.004M/s ( 0.050M/s/cpu) uretprobe-nop ( 1 cpus): 1.979 ± 0.005M/s ( 1.979M/s/cpu) uretprobe-nop ( 2 cpus): 2.361 ± 0.005M/s ( 1.180M/s/cpu) uretprobe-nop ( 4 cpus): 2.309 ± 0.002M/s ( 0.577M/s/cpu) uretprobe-nop ( 8 cpus): 2.253 ± 0.001M/s ( 0.282M/s/cpu) uretprobe-nop (16 cpus): 2.007 ± 0.000M/s ( 0.125M/s/cpu) uretprobe-nop (32 cpus): 1.624 ± 0.003M/s ( 0.051M/s/cpu) uretprobe-nop (64 cpus): 2.149 ± 0.001M/s ( 0.034M/s/cpu) Up to second-to-last patch (i.e., SRCU-based optimizations) =========================================================== uprobe-nop ( 1 cpus): 3.276 ± 0.005M/s ( 3.276M/s/cpu) uprobe-nop ( 2 cpus): 4.125 ± 0.002M/s ( 2.063M/s/cpu) uprobe-nop ( 4 cpus): 7.713 ± 0.002M/s ( 1.928M/s/cpu) uprobe-nop ( 8 cpus): 8.097 ± 0.006M/s ( 1.012M/s/cpu) uprobe-nop (16 cpus): 6.501 ± 0.056M/s ( 0.406M/s/cpu) uprobe-nop (32 cpus): 4.398 ± 0.084M/s ( 0.137M/s/cpu) uprobe-nop (64 cpus): 6.452 ± 0.000M/s ( 0.101M/s/cpu) uretprobe-nop ( 1 cpus): 2.055 ± 0.001M/s ( 2.055M/s/cpu) uretprobe-nop ( 2 cpus): 2.677 ± 0.000M/s ( 1.339M/s/cpu) uretprobe-nop ( 4 cpus): 4.561 ± 0.003M/s ( 1.140M/s/cpu) uretprobe-nop ( 8 cpus): 5.291 ± 0.002M/s ( 0.661M/s/cpu) uretprobe-nop (16 cpus): 5.065 ± 0.019M/s ( 0.317M/s/cpu) uretprobe-nop (32 cpus): 3.622 ± 0.003M/s ( 0.113M/s/cpu) uretprobe-nop (64 cpus): 3.723 ± 0.002M/s ( 0.058M/s/cpu) RCU Tasks Trace =============== uprobe-nop ( 1 cpus): 3.396 ± 0.002M/s ( 3.396M/s/cpu) uprobe-nop ( 2 cpus): 4.271 ± 0.006M/s ( 2.135M/s/cpu) uprobe-nop ( 4 cpus): 8.499 ± 0.015M/s ( 2.125M/s/cpu) uprobe-nop ( 8 cpus): 10.355 ± 0.028M/s ( 1.294M/s/cpu) uprobe-nop (16 cpus): 7.615 ± 0.099M/s ( 0.476M/s/cpu) uprobe-nop (32 cpus): 4.430 ± 0.007M/s ( 0.138M/s/cpu) uprobe-nop (64 cpus): 6.887 ± 0.020M/s ( 0.108M/s/cpu) uretprobe-nop ( 1 cpus): 2.174 ± 0.001M/s ( 2.174M/s/cpu) uretprobe-nop ( 2 cpus): 2.853 ± 0.001M/s ( 1.426M/s/cpu) uretprobe-nop ( 4 cpus): 4.913 ± 0.002M/s ( 1.228M/s/cpu) uretprobe-nop ( 8 cpus): 5.883 ± 0.002M/s ( 0.735M/s/cpu) uretprobe-nop (16 cpus): 5.147 ± 0.001M/s ( 0.322M/s/cpu) uretprobe-nop (32 cpus): 3.738 ± 0.008M/s ( 0.117M/s/cpu) uretprobe-nop (64 cpus): 4.397 ± 0.002M/s ( 0.069M/s/cpu) For baseline vs SRCU, peak througput increased from 3.7 M/s (million uprobe triggerings per second) up to about 8 M/s. For uretprobes it's a bit more modest with bump from 2.4 M/s to 5 M/s. For SRCU vs RCU Tasks Trace, peak throughput for uprobes increases further from 8 M/s to 10.3 M/s (+28%!), and for uretprobes from 5.3 M/s to 5.8 M/s (+11%), as we have more work to do on uretprobes side. Even single-thread (no contention) performance is slightly better: 3.276 M/s to 3.396 M/s (+3.5%) for uprobes, and 2.055 M/s to 2.174 M/s (+5.8%) for uretprobes. [0] https://lore.kernel.org/linux-trace-kernel/20240711110235.098009979@infradead.org/ [1] https://lore.kernel.org/linux-trace-kernel/20240729134444.GA12293@redhat.com/ [2] https://github.com/libbpf/libbpf-bootstrap/tree/uprobe-stress v2->v3: - undid rcu and rb_node fields colocation which were causing crashes (Oleg); - ensure synchronize_srcu() on registration failure in patch #4 (Oleg); v1->v2: - added back missed kfree() in patch #1 (Oleg); - forgot the rest, but there were a few small things here and there. Andrii Nakryiko (10): uprobes: revamp uprobe refcounting and lifetime management uprobes: protected uprobe lifetime with SRCU uprobes: get rid of enum uprobe_filter_ctx in uprobe filter callbacks uprobes: travers uprobe's consumer list locklessly under SRCU protection uprobes: perform lockless SRCU-protected uprobes_tree lookup uprobes: switch to RCU Tasks Trace flavor for better performance uprobes: SRCU-protect uretprobe lifetime (with timeout) uprobes: implement SRCU-protected lifetime for single-stepped uprobe mm: add SLAB_TYPESAFE_BY_RCU to files_cache uprobes: add speculative lockless VMA to inode resolution Peter Zijlstra (2): perf/uprobe: split uprobe_unregister() rbtree: provide rb_find_rcu() / rb_find_add_rcu() Suren Baghdasaryan (1): mm: introduce mmap_lock_speculation_{start|end} include/linux/mm_types.h | 3 + include/linux/mmap_lock.h | 53 +- include/linux/rbtree.h | 67 ++ include/linux/uprobes.h | 73 +- kernel/events/uprobes.c | 733 +++++++++++++----- kernel/fork.c | 7 +- kernel/trace/bpf_trace.c | 8 +- kernel/trace/trace_uprobe.c | 15 +- .../selftests/bpf/bpf_testmod/bpf_testmod.c | 3 +- 9 files changed, 722 insertions(+), 240 deletions(-) Reviewed-by: Oleg Nesterov