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[66.63.167.143]) by mx.google.com with ESMTPS id g8si1720045ybo.375.2019.04.08.12.44.51 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 08 Apr 2019 12:44:52 -0700 (PDT) Received-SPF: pass (google.com: domain of james.bottomley@hansenpartnership.com designates 66.63.167.143 as permitted sender) client-ip=66.63.167.143; Authentication-Results: mx.google.com; dkim=fail header.i=@hansenpartnership.com header.s=20151216 header.b=kiI+V52P; dkim=fail header.i=@hansenpartnership.com header.s=20151216 header.b=kiI+V52P; spf=pass (google.com: domain of james.bottomley@hansenpartnership.com designates 66.63.167.143 as permitted sender) smtp.mailfrom=James.Bottomley@hansenpartnership.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=hansenpartnership.com Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 904368EE0ED; Mon, 8 Apr 2019 12:44:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1554752690; bh=lyWACdjW8xXzOPzGVObCfEmFjzL6duzlAMiIgLxC8o0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=kiI+V52PeJKs9CJMKxxWogJp0itLjuVeEQGJvWOFMNeOCNs33jKwG7kplrTaHiO51 vQ4O12gJapy3f8aXXr3p7N5LqLSpdevFhigmDJuScehSeaDlcNqmgWD7cbiB0IpoBm b1nh4lURJ22jePI8DpSA92sPyFKK4XVSdwHtgFek= Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jbt7uxPM6yKR; Mon, 8 Apr 2019 12:44:50 -0700 (PDT) Received: from [172.16.10.48] (unknown [63.64.162.234]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id B2FFB8EE062; Mon, 8 Apr 2019 12:44:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1554752690; bh=lyWACdjW8xXzOPzGVObCfEmFjzL6duzlAMiIgLxC8o0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=kiI+V52PeJKs9CJMKxxWogJp0itLjuVeEQGJvWOFMNeOCNs33jKwG7kplrTaHiO51 vQ4O12gJapy3f8aXXr3p7N5LqLSpdevFhigmDJuScehSeaDlcNqmgWD7cbiB0IpoBm b1nh4lURJ22jePI8DpSA92sPyFKK4XVSdwHtgFek= Message-ID: <1554752688.3634.6.camel@HansenPartnership.com> Subject: Re: Memory management broken by "mm: reclaim small amounts of memory when an external fragmentation event occurs" From: James Bottomley To: Helge Deller , Mel Gorman , Mikulas Patocka Cc: Andrew Morton , John David Anglin , linux-parisc@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , Andrea Arcangeli , Zi Yan Date: Mon, 08 Apr 2019 12:44:48 -0700 In-Reply-To: <1aca1299-8713-3d54-7c5e-adf791509987@gmx.de> References: <20190408095224.GA18914@techsingularity.net> <1554733749.3137.6.camel@HansenPartnership.com> <1aca1299-8713-3d54-7c5e-adf791509987@gmx.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit 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 Mon, 2019-04-08 at 17:22 +0200, Helge Deller wrote: > On 08.04.19 16:29, James Bottomley wrote: > > On Mon, 2019-04-08 at 10:52 +0100, Mel Gorman wrote: > > > First, if pa-risc is !NUMA then why are separate local ranges > > > represented as separate nodes? Is it because of DISCONTIGMEM or > > > something else? DISCONTIGMEM is before my time so I'm not > > > familiar with it and I consider it "essentially dead" but the > > > arch init code seems to setup pgdats for each physical contiguous > > > range so it's a possibility. The most likely explanation is pa- > > > risc does not have hardware with addressing limitations smaller > > > than the CPUs physical address limits and it's possible to have > > > more ranges than available zones but clarification would be nice. > > > > Let me try, since I remember the ancient history. In the early > > days, there had to be a single mem_map array covering all of > > physical memory. Some pa-risc systems had huge gaps in the > > physical memory; I think one gap was somewhere around 1GB, so this > > lead us to wasting huge amounts of space in mem_map on non-existent > > memory. What CONFIG_DISCONTIGMEM did was allow you to represent > > this discontinuity on a non-NUMA system using numa nodes, so we > > effectively got one node per discontiguous range. It's hacky, but > > it worked. I thought we finally got converted to sparsemem by the > > NUMA people, but I can't find the commit. > > James, you tried once: > https://patchwork.kernel.org/patch/729441/ Ah, so what I was remembering as someone else's problem was, in fact, my problem? Hey, I should bottle my memory recall algorithms and sell them as executive training courses. > It seems we better should move over to sparsemem now? I think so. The basics of the patch likely apply and hopefully in the intervening 8 years some of the problems I identified have been fixed. James