From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 9855F828E5 for ; Mon, 4 Apr 2016 17:22:35 -0400 (EDT) Received: by mail-pa0-f45.google.com with SMTP id zm5so151935902pac.0 for ; Mon, 04 Apr 2016 14:22:35 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id 79si2376936pfm.61.2016.04.04.14.22.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Apr 2016 14:22:34 -0700 (PDT) Date: Mon, 4 Apr 2016 14:22:33 -0700 From: Andrew Morton Subject: Re: [PATCH 2/3] mm: filemap: only do access activations on reads Message-Id: <20160404142233.cfdea284b8107768fb359efd@linux-foundation.org> In-Reply-To: <1459790018-6630-3-git-send-email-hannes@cmpxchg.org> References: <1459790018-6630-1-git-send-email-hannes@cmpxchg.org> <1459790018-6630-3-git-send-email-hannes@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andres Freund , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com On Mon, 4 Apr 2016 13:13:37 -0400 Johannes Weiner wrote: > Andres Freund observed that his database workload is struggling with > the transaction journal creating pressure on frequently read pages. > > Access patterns like transaction journals frequently write the same > pages over and over, but in the majority of cases those pages are > never read back. There are no caching benefits to be had for those > pages, so activating them and having them put pressure on pages that > do benefit from caching is a bad choice. Read-after-write is a pretty common pattern: temporary files for example. What are the opportunities for regressions here? Did you consider providing userspace with a way to hint "this file is probably write-then-not-read"? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org