From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f174.google.com (mail-ob0-f174.google.com [209.85.214.174]) by kanga.kvack.org (Postfix) with ESMTP id 6C8556B0038 for ; Thu, 25 Jun 2015 21:31:03 -0400 (EDT) Received: by obbop1 with SMTP id op1so58227910obb.2 for ; Thu, 25 Jun 2015 18:31:03 -0700 (PDT) Received: from mail-oi0-x22a.google.com (mail-oi0-x22a.google.com. [2607:f8b0:4003:c06::22a]) by mx.google.com with ESMTPS id zc1si16094091obc.95.2015.06.25.18.31.02 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jun 2015 18:31:02 -0700 (PDT) Received: by oiyy130 with SMTP id y130so65465958oiy.0 for ; Thu, 25 Jun 2015 18:31:02 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150626005808.GA5704@swordfish> References: <20150624152518.d3a5408f2bde405df1e6e5c4@linux-foundation.org> <20150626005808.GA5704@swordfish> Date: Thu, 25 Jun 2015 18:31:02 -0700 Message-ID: Subject: Re: extremely long blockages when doing random writes to SSD From: Luigi Semenzato Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Andrew Morton , Linux Memory Management List We're using CFQ. CONFIG_DEFAULT_IOSCHED="cfq" ... CONFIG_IOSCHED_CFQ=y CONFIG_IOSCHED_DEADLINE=y CONFIG_IOSCHED_NOOP=y On Thu, Jun 25, 2015 at 5:58 PM, Sergey Senozhatsky wrote: > Hello, > > On (06/25/15 11:24), Luigi Semenzato wrote: >> I looked at this some more and I am not sure that there is any bug, or >> other possible tuning. >> >> While the random-write process runs, iostat -x -k 1 reports these numbers: >> >> average queue size: around 300 >> average write wait: typically 200 to 400 ms, but can be over 1000 ms >> average read wait: typically 50 to 100 ms >> >> (more info at crbug.com/414709) >> >> The read latency may be enough to explain the jank. In addition, the >> browser can do fsyncs, and I think that those will block for a long >> time. >> >> Ionice doesn't seem to make a difference. I suspect that once the >> blocks are in the output queue, it's first-come/first-serve. Is this >> correct or am I confused? >> >> We can fix this on the application side but only partially. The OS >> version updater can use O_SYNC. The problem is that his can happen in >> a number of situations, such as when simply downloading a large file, >> and in other code we don't control. >> > > do you use CONFIG_IOSCHED_DEADLINE or CONFIG_IOSCHED_CFQ? > > -ss -- 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