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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 80455C43464 for ; Sat, 19 Sep 2020 04:44:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AE2D422211 for ; Sat, 19 Sep 2020 04:44:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="gSbClo97" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE2D422211 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E8C1A6B005C; Sat, 19 Sep 2020 00:44:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E154C6B005D; Sat, 19 Sep 2020 00:44:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D054C6B0062; Sat, 19 Sep 2020 00:44:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0227.hostedemail.com [216.40.44.227]) by kanga.kvack.org (Postfix) with ESMTP id B700E6B005C for ; Sat, 19 Sep 2020 00:44:19 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 8277A3630 for ; Sat, 19 Sep 2020 04:44:19 +0000 (UTC) X-FDA: 77278569438.19.walk60_33020c727131 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin19.hostedemail.com (Postfix) with ESMTP id 6E0791AD1BA for ; Sat, 19 Sep 2020 04:44:19 +0000 (UTC) X-HE-Tag: walk60_33020c727131 X-Filterd-Recvd-Size: 3091 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Sat, 19 Sep 2020 04:44:18 +0000 (UTC) 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=eUq4iAXCgmFRQuJG0LnzSDMdVRozT7gWX2kuRsCkalg=; b=gSbClo97rMqgVp1lVlT/Lan5kn Sk7fMmRclfGNJfh6EwNI7gK7TPAkF+1VBfLHxRIw9+vRa6CNbD6YslYLCWU6924xhBw3i1+VLFOBo KLTOtV/e08d0DyTIMNhi3QRsy7x7TImPyd58y/0fenwah9pZwpPRAoN19ri40HdQGc35cenMxHm/t hnQtHXyznv+NLgXHNvhOmwVRoVN7obH3346uF7Mq2gGO6yCCe7GypOD1THHY+mhE/6rbY8RzFLy0I oHqg1NvQUyEltMq3Qubls05CH3qGElWTCqCPVExyOJcOCwf0X6Wa3kSbl9QQWcjSkpvX+Kq9KnnaJ ZHEQx8Ug==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kJUjI-0006WP-L8; Sat, 19 Sep 2020 04:44:08 +0000 Date: Sat, 19 Sep 2020 05:44:08 +0100 From: Matthew Wilcox To: Andrew Morton Cc: alex.shi@linux.alibaba.com, cai@lca.pw, hannes@cmpxchg.org, hughd@google.com, linux-mm@kvack.org, mhocko@suse.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, shakeelb@google.com, shy828301@gmail.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: Re: [patch 04/15] shmem: shmem_writepage() split unlikely i915 THP Message-ID: <20200919044408.GL32101@casper.infradead.org> References: <20200918211925.7e97f0ef63d92f5cfe5ccbc5@linux-foundation.org> <20200919042009.bomzxmrg7%akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200919042009.bomzxmrg7%akpm@linux-foundation.org> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 18, 2020 at 09:20:09PM -0700, Andrew Morton wrote: > LRU page reclaim always splits the shmem huge page first: I'd prefer not > to demand that of i915, so check and split compound in shmem_writepage(). Sorry for not checking this earlier, but I don't think this is right. for (i = 0; i < obj->base.size >> PAGE_SHIFT; i++) { ... if (!page_mapped(page) && clear_page_dirty_for_io(page)) { ... ret = mapping->a_ops->writepage(page, &wbc); so we cleared the dirty bit on the entire hugepage, but then split it after clearing the dirty bit, so the subpages are now not dirty. I think we'll lose writes as a result? At least we won't swap pages out that deserve to be paged out. > > - VM_BUG_ON_PAGE(PageCompound(page), page); > + /* > + * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "force", > + * then drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages, > + * and its shmem_writeback() needs them to be split when swapping. > + */ > + if (PageTransCompound(page)) > + if (split_huge_page(page) < 0) > + goto redirty; > + > BUG_ON(!PageLocked(page)); > mapping = page->mapping; > index = page->index; > _ >