From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E534EC433DB for ; Mon, 28 Dec 2020 16:32:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4886208D5 for ; Mon, 28 Dec 2020 16:32:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2441881AbgL1Qbw (ORCPT ); Mon, 28 Dec 2020 11:31:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:60790 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730489AbgL1NEj (ORCPT ); Mon, 28 Dec 2020 08:04:39 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6B44322582; Mon, 28 Dec 2020 13:03:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1609160639; bh=dk4t7gfGTMw5YQaATINpxtv/8lOtwfdQJeyfNPjtTl4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DuTukr2UQrqgDZn8lobX1S0U1J4vMTsN1VSj/XqIzfkvoIZpZZ6glTIQeL1LTDLs9 Cb3eqGyl8CTjM8zlZ4m02BCZmvuIkKtCnIC+6iovxH3xeIk6B/Z+2rP2NnUt6obuZq Zr5COOFVFHGKgeQhIWV4WIuovFaSAPg6a9sxEp2g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, NeilBrown , Trond Myklebust , Sasha Levin Subject: [PATCH 4.9 089/175] NFS: switch nfsiod to be an UNBOUND workqueue. Date: Mon, 28 Dec 2020 13:49:02 +0100 Message-Id: <20201228124857.561327172@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201228124853.216621466@linuxfoundation.org> References: <20201228124853.216621466@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: NeilBrown [ Upstream commit bf701b765eaa82dd164d65edc5747ec7288bb5c3 ] nfsiod is currently a concurrency-managed workqueue (CMWQ). This means that workitems scheduled to nfsiod on a given CPU are queued behind all other work items queued on any CMWQ on the same CPU. This can introduce unexpected latency. Occaionally nfsiod can even cause excessive latency. If the work item to complete a CLOSE request calls the final iput() on an inode, the address_space of that inode will be dismantled. This takes time proportional to the number of in-memory pages, which on a large host working on large files (e.g.. 5TB), can be a large number of pages resulting in a noticable number of seconds. We can avoid these latency problems by switching nfsiod to WQ_UNBOUND. This causes each concurrent work item to gets a dedicated thread which can be scheduled to an idle CPU. There is precedent for this as several other filesystems use WQ_UNBOUND workqueue for handling various async events. Signed-off-by: NeilBrown Fixes: ada609ee2ac2 ("workqueue: use WQ_MEM_RECLAIM instead of WQ_RESCUER") Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index 851274b25d394..6c0035761d170 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -1995,7 +1995,7 @@ static int nfsiod_start(void) { struct workqueue_struct *wq; dprintk("RPC: creating workqueue nfsiod\n"); - wq = alloc_workqueue("nfsiod", WQ_MEM_RECLAIM, 0); + wq = alloc_workqueue("nfsiod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0); if (wq == NULL) return -ENOMEM; nfsiod_workqueue = wq; -- 2.27.0