Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752434AbbHUSRr (ORCPT ); Fri, 21 Aug 2015 14:17:47 -0400 Received: from mail-io0-f182.google.com ([209.85.223.182]:36733 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752153AbbHUSRq (ORCPT ); Fri, 21 Aug 2015 14:17:46 -0400 MIME-Version: 1.0 In-Reply-To: <1440177121-12741-1-git-send-email-klamm@yandex-team.ru> References: <1440177121-12741-1-git-send-email-klamm@yandex-team.ru> Date: Fri, 21 Aug 2015 11:17:43 -0700 X-Google-Sender-Auth: f0DLPOZ-OjCrX7pDHv7PC9LtWAo Message-ID: Subject: Re: [PATCH] mm: use only per-device readahead limit From: Linus Torvalds To: Roman Gushchin Cc: linux-mm , Linux Kernel Mailing List , Raghavendra K T , Jan Kara , Wu Fengguang , David Rientjes , Andrew Morton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 976 Lines: 24 On Fri, Aug 21, 2015 at 10:12 AM, Roman Gushchin wrote: > > There are devices, which require custom readahead limit. > For instance, for RAIDs it's calculated as number of devices > multiplied by chunk size times 2. So afaik, the default read-ahead size is 128kB, which is actually smaller than the old 512-page limit. Which means that you probably changed "ra_pages" somehow. Is it some system tool that does that automatically, and if so based on what, exactly? I'm also slightly worried about the fact that now the max read-ahead may actually be zero, and/or basically infinite (there's a ioctl to set it that only tests that it's not negative). Does everything react ok to that? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/