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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BA5AC433EF for ; Mon, 31 Jan 2022 04:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357604AbiAaEWu (ORCPT ); Sun, 30 Jan 2022 23:22:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229572AbiAaEWs (ORCPT ); Sun, 30 Jan 2022 23:22:48 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9617C061714; Sun, 30 Jan 2022 20:22:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=OLdzjKeQbAZ/xufoUOt+WpAslfh1hvc6hLdQ1kOi3Gs=; b=ho9BSG2IZhWlh0U5/kITCAulfO FbXaBXt8TzCbX2L4KRlFN3z48OolajKBQZNZLV5AXovZjARGAaZYQc1HD+7+vHTJaZT3qigW/CSs4 YcwOh70Rv5WZpt5/zAWqu22VwCXZfSVJ+x4QNA+yKbnjz+X0Xi2DQ7SHkdvE1RXMH0abbt6oynLxc LS2QsDoseyoMZYIpNOiVUcVhVD+K0daCBMV0HOa8Lc20fGXDTAOcZpAcCqifPHLZLUcOh/Itd7Nt3 HOuvJaTWwoeMUA2VJBk9y9uFIAuD9/r/Rr16Lhi3ztiPacF3dV/s2ys6xrNzVB06OxtGdAnA6tGr/ NsBq18pQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nEOD4-009Fmn-1e; Mon, 31 Jan 2022 04:22:34 +0000 Date: Mon, 31 Jan 2022 04:22:34 +0000 From: Matthew Wilcox To: NeilBrown Cc: Andrew Morton , Jeff Layton , Ilya Dryomov , Miklos Szeredi , Trond Myklebust , Anna Schumaker , linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] nfs: remove reliance on bdi congestion Message-ID: References: <164360127045.4233.2606812444285122570.stgit@noble.brown> <164360183350.4233.691070075155620959.stgit@noble.brown> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <164360183350.4233.691070075155620959.stgit@noble.brown> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 31, 2022 at 03:03:53PM +1100, NeilBrown wrote: > - .writepage to return AOP_WRITEPAGE_ACTIVATE if WB_SYNC_NONE > and the flag is set. Is this actually useful? I ask because Dave Chinner believes the call to ->writepage in vmscan to be essentially unused. See commit 21b4ee7029c9, and I had a followup discussion with him on IRC: dchinner: did you gather any stats on how often ->writepage was being called by pageout() before "xfs: drop ->writepage completely" was added? willy: Never saw it on XFS in 3 years in my test environment... I don't ever recall seeing the memory reclaim guards we put on ->writepage in XFS ever firing - IIRC they'd been there for the best part of a decade. not so much the WARN_ON firing but the case where it actually calls iomap_writepage willy: I mean both - I was running with a local patch that warned on writepage for a long time, regardless of where it was called from. I can believe things are different for a network filesystem, or maybe XFS does background writeback better than other filesystems, but it would be intriguing to be able to get rid of ->writepage altogether (or at least from pageout(); migrate.c may be a thornier proposition).