From: Norbert Preining Subject: Re: Ext4 slow on links Date: Wed, 20 Jun 2012 14:18:44 +0900 Message-ID: <20120620051844.GA7829@gamma.logic.tuwien.ac.at> References: <20120620002014.GA25471@gamma.logic.tuwien.ac.at> <4FE14034.6070800@redhat.com> <20120620002014.GA25471@gamma.logic.tuwien.ac.at> <20120620021912.GA26323@thunk.org> <20120620033831.GA2395@gamma.logic.tuwien.ac.at> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ted Ts'o , Eric Sandeen , "linux-ext4@vger.kernel.org" To: Eric Sandeen Return-path: Received: from mx.logic.tuwien.ac.at ([128.130.175.19]:43877 "EHLO mx.logic.tuwien.ac.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751342Ab2FTFSt (ORCPT ); Wed, 20 Jun 2012 01:18:49 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Eric, On Di, 19 Jun 2012, Eric Sandeen wrote: > blktrace of the actions would show you something interesting as well. I tried to understand the output, but didn't get any information that tells me something. I rebooted into single user mode, started blktrace on sda, then run time ls -l /..../dir/with/links/ >/dev/null, stopped the blktrace. Then I run blkparse and btt etc to generate a variety of data. Here are some output of the btt run: ==================== All Devices ==================== ALL MIN AVG MAX N --------------- ------------- ------------- ------------- ----------- Q2Q 0.000002654 0.009716548 6.594440648 8953 Q2G 0.000001047 0.000001825 0.000011594 8913 G2I 0.000000908 0.000001561 0.000234317 8913 Q2M 0.000000908 0.000001046 0.000001536 41 I2D 0.000005378 0.001040528 1.572900300 8913 M2D 0.000014527 0.038626776 1.572908333 41 D2C 0.000098337 0.009050273 0.053790446 8954 Q2C 0.000108394 0.010266282 1.577191424 8954 ==================== Device Overhead ==================== DEV | Q2G G2I Q2M I2D D2C ---------- | --------- --------- --------- --------- --------- ( 8, 0) | 0.0177% 0.0151% 0.0000% 10.0890% 88.1553% ---------- | --------- --------- --------- --------- --------- Overall | 0.0177% 0.0151% 0.0000% 10.0890% 88.1553% ==================== Device Merge Information ==================== DEV | #Q #D Ratio | BLKmin BLKavg BLKmax Total ---------- | -------- -------- ------- | -------- -------- -------- -------- ( 8, 0) | 8954 8913 1.0 | 8 9 1024 86872 ==================== Device Q2Q Seek Information ==================== DEV | NSEEKS MEAN MEDIAN | MODE ---------- | --------------- --------------- --------------- | --------------- ( 8, 0) | 8954 193362127.3 0 | 0(538) ---------- | --------------- --------------- --------------- | --------------- Overall | NSEEKS MEAN MEDIAN | MODE Average | 8954 193362127.3 0 | 0(538) ==================== Device D2D Seek Information ==================== DEV | NSEEKS MEAN MEDIAN | MODE ---------- | --------------- --------------- --------------- | --------------- ( 8, 0) | 8913 194044831.4 0 | 0(497) ---------- | --------------- --------------- --------------- | --------------- Overall | NSEEKS MEAN MEDIAN | MODE Average | 8913 194044831.4 0 | 0(497) ==================== Plug Information ==================== DEV | # Plugs # Timer Us | % Time Q Plugged ---------- | ---------- ---------- | ---------------- ( 8, 0) | 81( 0) | 0.002663579% DEV | IOs/Unp IOs/Unp(to) ---------- | ---------- ---------- ( 8, 0) | 1.2 0.0 ---------- | ---------- ---------- Overall | IOs/Unp IOs/Unp(to) Average | 1.2 0.0 ==================== Active Requests At Q Information ==================== DEV | Avg Reqs @ Q ---------- | ------------- ( 8, 0) | 0.1 ..... I don't know if that shows anything of interest, but if you need more, and want to waste a bit of time looking at the data, I have uploaded everything created into http://www.logic.at/people/preining/BlkParse.tar.gz size 5090853 md5sum 46db8455a04dcc4a602e34d21eecc6bd In any case, thanks for your patience and support Norbert ------------------------------------------------------------------------ Norbert Preining preining@{jaist.ac.jp, logic.at, debian.org} JAIST, Japan TeX Live & Debian Developer DSA: 0x09C5B094 fp: 14DF 2E6C 0307 BE6D AD76 A9C0 D2BF 4AA3 09C5 B094 ------------------------------------------------------------------------ KIRBY (n.) Small but repulsive piece of food prominently attached to a person's face or clothing. See also CHIPPING ONGAR. --- Douglas Adams, The Meaning of Liff