From mboxrd@z Thu Jan 1 00:00:00 1970 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 B2C08138E; Wed, 10 Apr 2024 23:22:02 +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=1712791322; cv=none; b=tJQi0mhYzkEBDXgOsy4lqkzXtekv+AK/eEJP+xfIGJILZzzDKwr3rIZdRZ0nQdi/trM7g8I95DH3Xh6KtgcDFmhE3KynS6dfFGQwYoRbWoO2LVMD6GVumE+bsU/Vi+aatiRACJky36MG8y2hOS0LBZg4mhQZmEPZxt+JgtqomqE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712791322; c=relaxed/simple; bh=vZjbMD6Jt287ODnsZPSuTjU7DsqVXUkB99DDCx9Tfrg=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=m9j8l9V2H1zGgCHQC3R5o0Pdt/CyBhvgDC5z8frKKoHBuWGfBVNCGRxZbDhb7p/4DBcXGq4xgDFSmYOZUqU8fE8mHsRQa7o2efOsJEHOOkd79F4ZhQzogbD9MrIr+4IFzg8dXAruzzXy7hCNQJZzd5WJWilZWPQ6peGiGXKAt+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MbHNuHzs; 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="MbHNuHzs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB274C433C7; Wed, 10 Apr 2024 23:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1712791322; bh=vZjbMD6Jt287ODnsZPSuTjU7DsqVXUkB99DDCx9Tfrg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=MbHNuHzs8+ZKHxrg1xfuZ5COlcBxcxARniCXIPFp6Q4EZRxWJuwxe9/7ndRzpfblU To42eYEt+GeoNiMWxDCUG7+7IKGRTYk+KPpxTSDTanV9dZ0N1fehrb7jHTLgxn7Fry rhZSwIwRf2EqBZ0LBdrzZaOKWIS5c9mxP7dLyQCNvo+gtwBNNrmHoM/bGtbsbONN7n UH8XMmDxO3wdqFs4YP2GnX0h1ieR4Ne6gJKOaT24773nEla4CACSNBiHHuT7WzPns2 MuOK6ItgEaIURhf7Mw9Tr+uvqbQ93qeKykTkk4VaVovQsjR2AovHWtAmmsdhkIw5XZ gnUKnqD0kHeUQ== Date: Thu, 11 Apr 2024 08:21:56 +0900 From: Masami Hiramatsu (Google) To: Jonthan Haslam Cc: Andrii Nakryiko , linux-trace-kernel@vger.kernel.org, andrii@kernel.org, bpf@vger.kernel.org, rostedt@goodmis.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] uprobes: reduce contention on uprobes_tree access Message-Id: <20240411082156.6613cf4dc03129ea1183ab88@kernel.org> In-Reply-To: References: <20240321145736.2373846-1-jonathan.haslam@gmail.com> <20240325120323.ec3248d330b2755e73a6571e@kernel.org> <20240327084245.a890ae12e579f0be1902ae4a@kernel.org> <54jakntmdyedadce7yrf6kljcjapbwyoqqt26dnllrqvs3pg7x@itra4a2ikgqw> <20240328091841.ce9cc613db375536de843cfb@kernel.org> <20240330093631.72273967ba818cb16aeb58b6@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 10 Apr 2024 11:38:11 +0100 Jonthan Haslam wrote: > Hi Masami, > > > > > Which is why I was asking to land this patch as is, as it relieves the > > > > scalability pains in production and is easy to backport to old > > > > kernels. And then we can work on batched APIs and switch to per-CPU rw > > > > semaphore. > > > > OK, then I'll push this to for-next at this moment. > > Please share if you have a good idea for the batch interface which can be > > backported. I guess it should involve updating userspace changes too. > > Did you (or anyone else) need anything more from me on this one so that it > can be pushed? I provided some benchmark numbers but happy to provide > anything else that may be required. Yeah, if you can update with the result, it looks better to me. Or, can I update the description? Thank you, > > Thanks! > > Jon. > > > > > Thank you! > > > > > > > > > > So I hope you can reconsider and accept improvements in this patch, > > > > while Jonathan will keep working on even better final solution. > > > > Thanks! > > > > > > > > > I look forward to your formalized results :) > > > > > > > > > > > BTW, as part of BPF selftests, we have a multi-attach test for uprobes > > > and USDTs, reporting attach/detach timings: > > > $ sudo ./test_progs -v -t uprobe_multi_test/bench > > > bpf_testmod.ko is already unloaded. > > > Loading bpf_testmod.ko... > > > Successfully loaded bpf_testmod.ko. > > > test_bench_attach_uprobe:PASS:uprobe_multi_bench__open_and_load 0 nsec > > > test_bench_attach_uprobe:PASS:uprobe_multi_bench__attach 0 nsec > > > test_bench_attach_uprobe:PASS:uprobes_count 0 nsec > > > test_bench_attach_uprobe: attached in 0.120s > > > test_bench_attach_uprobe: detached in 0.092s > > > #400/5 uprobe_multi_test/bench_uprobe:OK > > > test_bench_attach_usdt:PASS:uprobe_multi__open 0 nsec > > > test_bench_attach_usdt:PASS:bpf_program__attach_usdt 0 nsec > > > test_bench_attach_usdt:PASS:usdt_count 0 nsec > > > test_bench_attach_usdt: attached in 0.124s > > > test_bench_attach_usdt: detached in 0.064s > > > #400/6 uprobe_multi_test/bench_usdt:OK > > > #400 uprobe_multi_test:OK > > > Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED > > > Successfully unloaded bpf_testmod.ko. > > > > > > So it should be easy for Jonathan to validate his changes with this. > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > Jon. > > > > > > > > > > > > > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > BTW, how did you measure the overhead? I think spinlock overhead > > > > > > > > > will depend on how much lock contention happens. > > > > > > > > > > > > > > > > > > Thank you, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [0] https://docs.kernel.org/locking/spinlocks.html > > > > > > > > > > > > > > > > > > > > Signed-off-by: Jonathan Haslam > > > > > > > > > > --- > > > > > > > > > > kernel/events/uprobes.c | 22 +++++++++++----------- > > > > > > > > > > 1 file changed, 11 insertions(+), 11 deletions(-) > > > > > > > > > > > > > > > > > > > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > > > > > > > > > > index 929e98c62965..42bf9b6e8bc0 100644 > > > > > > > > > > --- a/kernel/events/uprobes.c > > > > > > > > > > +++ b/kernel/events/uprobes.c > > > > > > > > > > @@ -39,7 +39,7 @@ static struct rb_root uprobes_tree = RB_ROOT; > > > > > > > > > > */ > > > > > > > > > > #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree) > > > > > > > > > > > > > > > > > > > > -static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */ > > > > > > > > > > +static DEFINE_RWLOCK(uprobes_treelock); /* serialize rbtree access */ > > > > > > > > > > > > > > > > > > > > #define UPROBES_HASH_SZ 13 > > > > > > > > > > /* serialize uprobe->pending_list */ > > > > > > > > > > @@ -669,9 +669,9 @@ static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) > > > > > > > > > > { > > > > > > > > > > struct uprobe *uprobe; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > uprobe = __find_uprobe(inode, offset); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return uprobe; > > > > > > > > > > } > > > > > > > > > > @@ -701,9 +701,9 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe) > > > > > > > > > > { > > > > > > > > > > struct uprobe *u; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + write_lock(&uprobes_treelock); > > > > > > > > > > u = __insert_uprobe(uprobe); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + write_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return u; > > > > > > > > > > } > > > > > > > > > > @@ -935,9 +935,9 @@ static void delete_uprobe(struct uprobe *uprobe) > > > > > > > > > > if (WARN_ON(!uprobe_is_active(uprobe))) > > > > > > > > > > return; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + write_lock(&uprobes_treelock); > > > > > > > > > > rb_erase(&uprobe->rb_node, &uprobes_tree); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + write_unlock(&uprobes_treelock); > > > > > > > > > > RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ > > > > > > > > > > put_uprobe(uprobe); > > > > > > > > > > } > > > > > > > > > > @@ -1298,7 +1298,7 @@ static void build_probe_list(struct inode *inode, > > > > > > > > > > min = vaddr_to_offset(vma, start); > > > > > > > > > > max = min + (end - start) - 1; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > n = find_node_in_range(inode, min, max); > > > > > > > > > > if (n) { > > > > > > > > > > for (t = n; t; t = rb_prev(t)) { > > > > > > > > > > @@ -1316,7 +1316,7 @@ static void build_probe_list(struct inode *inode, > > > > > > > > > > get_uprobe(u); > > > > > > > > > > } > > > > > > > > > > } > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > /* @vma contains reference counter, not the probed instruction. */ > > > > > > > > > > @@ -1407,9 +1407,9 @@ vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long e > > > > > > > > > > min = vaddr_to_offset(vma, start); > > > > > > > > > > max = min + (end - start) - 1; > > > > > > > > > > > > > > > > > > > > - spin_lock(&uprobes_treelock); > > > > > > > > > > + read_lock(&uprobes_treelock); > > > > > > > > > > n = find_node_in_range(inode, min, max); > > > > > > > > > > - spin_unlock(&uprobes_treelock); > > > > > > > > > > + read_unlock(&uprobes_treelock); > > > > > > > > > > > > > > > > > > > > return !!n; > > > > > > > > > > } > > > > > > > > > > -- > > > > > > > > > > 2.43.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > Masami Hiramatsu (Google) > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > Masami Hiramatsu (Google) > > > > > > > > > > > > > > > -- > > > > > Masami Hiramatsu (Google) > > > > > > -- > > Masami Hiramatsu (Google) -- Masami Hiramatsu (Google)