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 614F71BD031; Tue, 12 Nov 2024 10:35:16 +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=1731407716; cv=none; b=JVL7zwGP+Ae39Aiu1WfZ3jtz8UHAVmOHIBzNdUp3NlVd8Vtj2ZeZuP0VhQBb247hLfuC22nP4pVgnfYTQsVg/fEMAHu+ER778HOBrnkRBBfdIWbrWtyZ//FloYRBf/nXlYT2W3470kxeqbUEKYzX3TcjfTjb4IYc0Dq7a50CpmA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731407716; c=relaxed/simple; bh=/3CFN+gpkjFPllCJmcYm3Oa39TjLS2RcFpEOnhps6vs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qxLlxZILJNBi+ubI8i1+v5Y7fCM16k70gqQRX0FMhs2/a/rkiEf29e87vvGKLrHmBCozZFIIeoz+tOwjTcr1kajwtjYYpoHrG4vmk+DPIWEtjElgjQlPSYQuX/LdmnL8NpxzVCwMD5HhIjgWWS3iH1mq/QW2lGieORR25ikAJok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=z0kIauE1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="z0kIauE1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5EA5EC4CECD; Tue, 12 Nov 2024 10:35:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1731407716; bh=/3CFN+gpkjFPllCJmcYm3Oa39TjLS2RcFpEOnhps6vs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=z0kIauE1otXXFcqxeKB+ykhDWhM1YMp1ZvytlkMdMEUgLDIJyfjH4GMR8cFNOcWmH qYSFZbTNs6ptYmLiDl8wew+qfViwquSxbYs5xPpzzMAH36fHJwnJv/4E3Vx2js8DUN O32xjOH4wHHwz3DbxwZeBcYrsJKKAcdpbrUF2MYU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mike Snitzer , Jeff Layton , Anna Schumaker , Sasha Levin Subject: [PATCH 6.6 028/119] nfs: avoid i_lock contention in nfs_clear_invalid_mapping Date: Tue, 12 Nov 2024 11:20:36 +0100 Message-ID: <20241112101849.790694412@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241112101848.708153352@linuxfoundation.org> References: <20241112101848.708153352@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Snitzer [ Upstream commit 867da60d463bb2a3e28c9235c487e56e96cffa00 ] Multi-threaded buffered reads to the same file exposed significant inode spinlock contention in nfs_clear_invalid_mapping(). Eliminate this spinlock contention by checking flags without locking, instead using smp_rmb and smp_load_acquire accordingly, but then take spinlock and double-check these inode flags. Also refactor nfs_set_cache_invalid() slightly to use smp_store_release() to pair with nfs_clear_invalid_mapping()'s smp_load_acquire(). While this fix is beneficial for all multi-threaded buffered reads issued by an NFS client, this issue was identified in the context of surprisingly low LOCALIO performance with 4K multi-threaded buffered read IO. This fix dramatically speeds up LOCALIO performance: before: read: IOPS=1583k, BW=6182MiB/s (6482MB/s)(121GiB/20002msec) after: read: IOPS=3046k, BW=11.6GiB/s (12.5GB/s)(232GiB/20001msec) Fixes: 17dfeb911339 ("NFS: Fix races in nfs_revalidate_mapping") Signed-off-by: Mike Snitzer Reviewed-by: Jeff Layton Signed-off-by: Anna Schumaker Signed-off-by: Sasha Levin --- fs/nfs/inode.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index ca76b0b51b779..d0fc3e80cd64c 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -206,12 +206,15 @@ void nfs_set_cache_invalid(struct inode *inode, unsigned long flags) nfs_fscache_invalidate(inode, 0); flags &= ~NFS_INO_REVAL_FORCED; - nfsi->cache_validity |= flags; + flags |= nfsi->cache_validity; + if (inode->i_mapping->nrpages == 0) + flags &= ~NFS_INO_INVALID_DATA; - if (inode->i_mapping->nrpages == 0) { - nfsi->cache_validity &= ~NFS_INO_INVALID_DATA; - nfs_ooo_clear(nfsi); - } else if (nfsi->cache_validity & NFS_INO_INVALID_DATA) { + /* pairs with nfs_clear_invalid_mapping()'s smp_load_acquire() */ + smp_store_release(&nfsi->cache_validity, flags); + + if (inode->i_mapping->nrpages == 0 || + nfsi->cache_validity & NFS_INO_INVALID_DATA) { nfs_ooo_clear(nfsi); } trace_nfs_set_cache_invalid(inode, 0); @@ -1340,6 +1343,13 @@ int nfs_clear_invalid_mapping(struct address_space *mapping) TASK_KILLABLE|TASK_FREEZABLE_UNSAFE); if (ret) goto out; + smp_rmb(); /* pairs with smp_wmb() below */ + if (test_bit(NFS_INO_INVALIDATING, bitlock)) + continue; + /* pairs with nfs_set_cache_invalid()'s smp_store_release() */ + if (!(smp_load_acquire(&nfsi->cache_validity) & NFS_INO_INVALID_DATA)) + goto out; + /* Slow-path that double-checks with spinlock held */ spin_lock(&inode->i_lock); if (test_bit(NFS_INO_INVALIDATING, bitlock)) { spin_unlock(&inode->i_lock); -- 2.43.0