From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E03213546EB; Tue, 15 Sep 2026 14:50:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789483804; cv=none; b=YV3rGa9jrlPb7z1z9L/AaQbgC5C500Kc0s++ZhtVI/3zIOji0/dbEIVkJeqyXzbWZ+tKO7gu/QM5U8iPaY3wh6jTbZ1dydAgbwKBQAdR7g/9UKJYkW+s+G0a5cc8INGlZkqdRLWXqgquY93okJ06CRqJ2aKosCul7/t/HKpAI6A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789483804; c=relaxed/simple; bh=4A9A3hR1WKTcyEVPLyAwjlzeAYK4rdx77bbKQx/pghw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=GITrHJVV4HsIf5KVktMmfg79JLCy7XQJR/MAKKSjKSYAExy+icKC/XmXuXZKjznHBWXk9kw1rpVExtH4WniIXOz+q50s2J9lKgnNZ+9j0nyXjq5iEIeIVel9YMWNClEX3eimsvXV1dGBAo3XhiQYlDdtzrIEk3wo5aTuSIXsmxc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YpHBmBli; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YpHBmBli" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A35A81F000FF; Tue, 15 Sep 2026 14:50:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789483802; bh=qPczooQUOvj610WKXgPZ6pJIJrriNp/5eVio72+yK30=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=YpHBmBliW53KUrKlsNrgzdy6wJ9/tOuXSsUsXd3Yaesp+PPjd3N1+D07ImLQ3bqSV +bQBfymRkdBgd0zmPlgNSTMiVLjQ2WAuyv78q9XXtYLg/rp1q3h04h2YzPDVj4e1a3 TIEJS1lhESge1WPZTRNaHP6M/fdgeu3rZugHMeUvR2vyVzqnybYQf/oQ3YaRybRF2O lLc7rNjYkzGPyvcZ5VoGuRvPKXN6oR6B7u602+NcmhrWlxeGLu6qwXNwqhbvyjtbBU sCmOPv1tikInrjHdYSb1VRM/pE7hAQ1g0aWWOk6p+dbd8+lcwjVNPdimjjfDD4zVTz 4i2QUBk7TJ9qA== Message-ID: <987d991af67bda38b98c7e0f9a50e78cfa3d2c3f.camel@kernel.org> Subject: Re: [PATCH v3 0/4] Reduce lock contention in the NFS client From: Jeff Layton To: Chuck Lever , Trond Myklebust , Anna Schumaker Cc: NeilBrown , Tim Menninger , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 15 Sep 2026 10:49:59 -0400 In-Reply-To: <20260915-performance-v3-0-ae26d460bfd3@kernel.org> References: <20260915-performance-v3-0-ae26d460bfd3@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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workload on 100GbE RDMA, roughly 150 RPC worker > threads drive the client, and lock contention dominates its CPU > profile: up to 53% of non-idle cycles are spent in > native_queued_spin_lock_slowpath. >=20 > Three locks account for that: reserve_lock on every XID > allocation, queue_lock on every submit and completion, and the > unbound worker pool lock on every enqueue and dequeue for rpciod, > nfsiod, and xprtiod. >=20 > This series addresses the first two. v2 also moved the three > workqueues to the WQ_AFFN_SMT scope. Tim Menninger reported an > intermittent throughput regression on a 96-CPU two-socket > NFS/RDMA client and bisected it to the rpciod scope change [1]. > The cause is still being worked out in that thread, so the scope > patches are withdrawn until it is understood. Until then, WQ_SYSFS > on all three workqueues lets an administrator set the scope from > user space. >=20 > [1] https://lore.kernel.org/linux-nfs/20260902204048.4100864-1-tmenninger= @everpuredata.com/ >=20 > --- > Changes in v3: > - Drop the WQ_AFFN_SMT scope patches (Tim Menninger's regression report) > - Rebase on v7.3-rc2 > - Link to v2: https://patch.msgid.link/20260902-performance-v2-0-b71c0c08= 2f9d@kernel.org >=20 > Changes in v2: > - Fix send bvec use-after-free in xprt_request_dequeue_xprt() (sashiko) > - Replace the three workqueue exports with workqueue_set_affn_scope() > - Split the WQ_SYSFS patch into SUNRPC and NFS patches > - Drop v1 patch 2: async completions in the submitter can deadlock > - Correct the pool cost and SMT group wording in the scope patches > - Link to v1: https://patch.msgid.link/20260831-performance-v1-0-8d9fd9b6= 7f96@kernel.org >=20 > --- > Chuck Lever (4): > SUNRPC: Use atomic_t for XID allocation > SUNRPC: Split recv_lock out of xprt->queue_lock > SUNRPC: Set WQ_SYSFS on rpciod and xprtiod > NFS: Set WQ_SYSFS on nfsiod >=20 > fs/nfs/inode.c | 3 +- > include/linux/sunrpc/xprt.h | 8 ++- > net/sunrpc/sched.c | 5 +- > net/sunrpc/svcsock.c | 6 +-- > net/sunrpc/xprt.c | 85 ++++++++++++++++++------= ------ > net/sunrpc/xprtrdma/rpc_rdma.c | 14 ++--- > net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 8 +-- > net/sunrpc/xprtsock.c | 18 +++---- > 8 files changed, 85 insertions(+), 62 deletions(-) > --- > base-commit: df2908090cda368b01ff43709f51890076c56157 > change-id: 20260831-performance-e465e621c1c0 >=20 > Best regards, > -- =20 > Chuck Lever Nice, straightforward performance wins! Reviewed-by: Jeff Layton