From nobody Thu Nov 28 13:45:00 2024 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 70B231CF29F; Tue, 1 Oct 2024 22:52:32 +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=1727823153; cv=none; b=my8ACXey4gZt2QdCdd2iHaenHNk3nYllLlkR+ucQs9YCnwuUpjaNQbvsynN1sOnJ92+52NZKhHzNGdMKnMU3APFezLrqE8o8dME21Hpy4iVHrnAlPEd/cqSbx154F0ysAcAm6Sd5K/9pWjWU1d21D4MoszQ5aNxyzrq+LaDLZ9s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727823153; c=relaxed/simple; bh=SCu4Evjr8HmMRl0UxC9lAbHfcHKC1A3FSblyNAiFGvA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=YwJ8nqxyjwD3CcBTzS5sLpMMmQTO/U/CMeTtZGtt6DjDfOagQ7TTVymogKnMS7bPhmiid0/B1hhsQrQwwhw9xzqOJY6YwZZJcP1EH5ey/3KnCrJom3dtdFY4/hKoScTTrSJUeldJXwoH8jb2ctAe2eLN2/UV6DYKWmm/twP4m0U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PFEgw2F6; 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="PFEgw2F6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8137C4CEC6; Tue, 1 Oct 2024 22:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727823151; bh=SCu4Evjr8HmMRl0UxC9lAbHfcHKC1A3FSblyNAiFGvA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PFEgw2F6J4Xe2BwH8mam8pcz1GB5lffSYNDNPEEEt3HlEnC0Qbkq2oTQyDSIMLiWj DSmiP6dU+c8qyjU8OVM6piYG2rCtLmkETgbiTqvCoFJoNkzPfCM9WUr13Wc4fOGmxx pVljwJGWFCLV4CGYelIjB8GVPXZmSGOs0L65Ytw5qAco2UcKI34w3q0XS2tH7fr0BP boAMJLHgBYFItKgyeclKrBcBkdmEVmXM5zZO8b/wiZIPKMa9G4TIoh0qWgO9cmjxRb hxd0LFCdgGurtO0LPY24vdhvphyP3bAIMTVbaeO7gHFtPiSKqz2ap0TzSaXsxaE8C5 OGOaFD3hzJrrQ== 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, mhocko@kernel.org, vbabka@suse.cz, mingo@kernel.org, Andrii Nakryiko Subject: [PATCH v2 tip/perf/core 5/5] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Date: Tue, 1 Oct 2024 15:52:07 -0700 Message-ID: <20241001225207.2215639-6-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241001225207.2215639-1-andrii@kernel.org> References: <20241001225207.2215639-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.384 =C2=B1 0.004M/s ( 3.384M/s/cpu) uprobe-nop ( 2 cpus): 5.456 =C2=B1 0.005M/s ( 2.728M/s/cpu) uprobe-nop ( 3 cpus): 7.863 =C2=B1 0.015M/s ( 2.621M/s/cpu) uprobe-nop ( 4 cpus): 9.442 =C2=B1 0.008M/s ( 2.360M/s/cpu) uprobe-nop ( 5 cpus): 11.036 =C2=B1 0.013M/s ( 2.207M/s/cpu) uprobe-nop ( 6 cpus): 10.884 =C2=B1 0.019M/s ( 1.814M/s/cpu) uprobe-nop ( 7 cpus): 7.897 =C2=B1 0.145M/s ( 1.128M/s/cpu) uprobe-nop ( 8 cpus): 10.021 =C2=B1 0.128M/s ( 1.253M/s/cpu) uprobe-nop (10 cpus): 9.932 =C2=B1 0.170M/s ( 0.993M/s/cpu) uprobe-nop (12 cpus): 8.369 =C2=B1 0.056M/s ( 0.697M/s/cpu) uprobe-nop (14 cpus): 8.678 =C2=B1 0.017M/s ( 0.620M/s/cpu) uprobe-nop (16 cpus): 7.392 =C2=B1 0.003M/s ( 0.462M/s/cpu) uprobe-nop (24 cpus): 5.326 =C2=B1 0.178M/s ( 0.222M/s/cpu) uprobe-nop (32 cpus): 5.426 =C2=B1 0.059M/s ( 0.170M/s/cpu) uprobe-nop (40 cpus): 5.262 =C2=B1 0.070M/s ( 0.132M/s/cpu) uprobe-nop (48 cpus): 6.121 =C2=B1 0.010M/s ( 0.128M/s/cpu) uprobe-nop (56 cpus): 6.252 =C2=B1 0.035M/s ( 0.112M/s/cpu) uprobe-nop (64 cpus): 7.644 =C2=B1 0.023M/s ( 0.119M/s/cpu) uprobe-nop (72 cpus): 7.781 =C2=B1 0.001M/s ( 0.108M/s/cpu) uprobe-nop (80 cpus): 8.992 =C2=B1 0.048M/s ( 0.112M/s/cpu) AFTER =3D=3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.534 =C2=B1 0.033M/s ( 3.534M/s/cpu) uprobe-nop ( 2 cpus): 6.701 =C2=B1 0.007M/s ( 3.351M/s/cpu) uprobe-nop ( 3 cpus): 10.031 =C2=B1 0.007M/s ( 3.344M/s/cpu) uprobe-nop ( 4 cpus): 13.003 =C2=B1 0.012M/s ( 3.251M/s/cpu) uprobe-nop ( 5 cpus): 16.274 =C2=B1 0.006M/s ( 3.255M/s/cpu) uprobe-nop ( 6 cpus): 19.563 =C2=B1 0.024M/s ( 3.261M/s/cpu) uprobe-nop ( 7 cpus): 22.696 =C2=B1 0.054M/s ( 3.242M/s/cpu) uprobe-nop ( 8 cpus): 24.534 =C2=B1 0.010M/s ( 3.067M/s/cpu) uprobe-nop (10 cpus): 30.475 =C2=B1 0.117M/s ( 3.047M/s/cpu) uprobe-nop (12 cpus): 33.371 =C2=B1 0.017M/s ( 2.781M/s/cpu) uprobe-nop (14 cpus): 38.864 =C2=B1 0.004M/s ( 2.776M/s/cpu) uprobe-nop (16 cpus): 41.476 =C2=B1 0.020M/s ( 2.592M/s/cpu) uprobe-nop (24 cpus): 64.696 =C2=B1 0.021M/s ( 2.696M/s/cpu) uprobe-nop (32 cpus): 85.054 =C2=B1 0.027M/s ( 2.658M/s/cpu) uprobe-nop (40 cpus): 101.979 =C2=B1 0.032M/s ( 2.549M/s/cpu) uprobe-nop (48 cpus): 110.518 =C2=B1 0.056M/s ( 2.302M/s/cpu) uprobe-nop (56 cpus): 117.737 =C2=B1 0.020M/s ( 2.102M/s/cpu) uprobe-nop (64 cpus): 124.613 =C2=B1 0.079M/s ( 1.947M/s/cpu) uprobe-nop (72 cpus): 133.239 =C2=B1 0.032M/s ( 1.851M/s/cpu) uprobe-nop (80 cpus): 142.037 =C2=B1 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). Note, results above assume that commit [0] from linux-trace tree is applied as well, otherwise it will limit scalability to about 10mln/s total throughput. [0] 10cdb82aa77f ("uprobes: turn trace_uprobe's nhit counter to be per-CP= U one") Suggested-by: Matthew Wilcox Signed-off-by: Andrii Nakryiko --- kernel/events/uprobes.c | 44 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 7bd9111b4e8b..960130275656 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2081,6 +2081,46 @@ static int is_trap_at_addr(struct mm_struct *mm, uns= igned long vaddr) return is_trap_insn(&opcode); } =20 +static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vadd= r) +{ + struct mm_struct *mm =3D current->mm; + struct uprobe *uprobe =3D NULL; + struct vm_area_struct *vma; + struct file *vm_file; + loff_t offset; + long seq; + + guard(rcu)(); + + if (!mmap_lock_speculation_start(mm, &seq)) + return NULL; + + vma =3D 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 =3D READ_ONCE(vma->vm_file); + if (!vm_file) + return NULL; + + offset =3D (loff_t)(vma->vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vma->vm_st= art); + uprobe =3D 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) { @@ -2088,6 +2128,10 @@ static struct uprobe *find_active_uprobe_rcu(unsigne= d long bp_vaddr, int *is_swb struct uprobe *uprobe =3D NULL; struct vm_area_struct *vma; =20 + uprobe =3D find_active_uprobe_speculative(bp_vaddr); + if (uprobe) + return uprobe; + mmap_read_lock(mm); vma =3D vma_lookup(mm, bp_vaddr); if (vma) { --=20 2.43.5