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[209.132.183.28]) by mx.google.com with ESMTPS id h5si5452542qkj.3.2019.04.06.10.27.01 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 06 Apr 2019 10:27:02 -0700 (PDT) Received-SPF: pass (google.com: domain of mpatocka@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of mpatocka@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mpatocka@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EE864356DB; Sat, 6 Apr 2019 17:27:00 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (file01.intranet.prod.int.rdu2.redhat.com [10.11.5.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 57D2E17F33; Sat, 6 Apr 2019 17:27:00 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (localhost [127.0.0.1]) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4) with ESMTP id x36HQxHu002281; Sat, 6 Apr 2019 13:26:59 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id x36HQvku002277; Sat, 6 Apr 2019 13:26:58 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Sat, 6 Apr 2019 13:26:57 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Mel Gorman , Andrew Morton , Helge Deller , "James E.J. Bottomley" , John David Anglin , linux-parisc@vger.kernel.org, linux-mm@kvack.org cc: Vlastimil Babka , Andrea Arcangeli , Zi Yan Subject: Re: Memory management broken by "mm: reclaim small amounts of memory when an external fragmentation event occurs" In-Reply-To: Message-ID: References: User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Sat, 06 Apr 2019 17:27:01 +0000 (UTC) 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 Sat, 6 Apr 2019, Mikulas Patocka wrote: > Hi > > The patch 1c30844d2dfe272d58c8fc000960b835d13aa2ac ("mm: reclaim small > amounts of memory when an external fragmentation event occurs") breaks > memory management on parisc. > > I have a parisc machine with 7GiB RAM, the chipset maps the physical > memory to three zones: > 0) Start 0x0000000000000000 End 0x000000003fffffff Size 1024 MB > 1) Start 0x0000000100000000 End 0x00000001bfdfffff Size 3070 MB > 2) Start 0x0000004040000000 End 0x00000040ffffffff Size 3072 MB > (but it is not NUMA) > > With the patch 1c30844d2, the kernel will incorrectly reclaim the first > zone when it fills up, ignoring the fact that there are two completely > free zones. Basiscally, it limits cache size to 1GiB. > > For example, if I run: > # dd if=/dev/sda of=/dev/null bs=1M count=2048 > > - with the proper kernel, there should be "Buffers - 2GiB" when this > command finishes. With the patch 1c30844d2, buffers will consume just 1GiB > or slightly more, because the kernel was incorrectly reclaiming them. > > Mikulas BTW, 3 years ago, there was exactly the same bug: https://marc.info/?l=linux-kernel&m=146472966215941&w=2 Mikulas