Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 13 Nov 2000 17:24:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 13 Nov 2000 17:24:25 -0500 Received: from sgi.SGI.COM ([192.48.153.1]:32581 "EHLO sgi.com") by vger.kernel.org with ESMTP id ; Mon, 13 Nov 2000 17:24:08 -0500 From: "LA Walsh" To: "lkml" Subject: writing out disk cache Date: Mon, 13 Nov 2000 13:52:39 -0800 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Another question that's been bugging me -- this is behavior that seems identical in 2216/2217 and not related to my ealier performance degredation post. I run VMware. It runs w/144Mg and writes out a 153M suspend file when I suspend it to disk. My system has a total of 512M, so the entire suspend file gets written to the disk buffers pronto (often under 1 second). But a 'sync' done afterwards can take anywhere from 20-40 seconds. vmstat shows a maximum b/o rate of 700, with 200-500 being typical. So, I know that the maximum write rate through the disk cache is close to 10,000 blocks/second. So why when the disk cache of a large file is 'sync'ed out, do I get such low b/o rates? Two sample 'vmstat 5' outputs during a sync were: 1 0 0 6292 13500 254572 165712 0 0 1 0 119 282 1 1 98 2 0 0 6292 13444 254572 165716 0 0 0 702 279 534 0 2 98 1 1 0 6292 13444 254572 165716 0 0 0 501 352 669 0 1 99 0 1 0 6292 13444 254572 165716 0 0 0 520 372 697 0 2 97 1 0 0 6292 13444 254572 165716 0 0 0 510 367 694 0 2 98 0 1 0 6292 13444 254572 165716 0 0 0 694 379 715 0 2 98 1 0 1 6292 13444 254572 165716 0 0 0 618 391 964 0 2 98 0 1 1 6292 13444 254572 165716 0 0 0 441 302 765 0 1 98 0 0 0 6292 13496 254572 165716 0 0 0 63 180 355 1 1 99 0 0 0 6292 13496 254572 165716 0 0 0 0 103 195 0 1 99 ----and 0 0 0 6228 18836 246036 167824 0 0 0 0 232 563 6 13 82 0 1 0 6228 18784 246036 167824 0 0 0 506 175 489 2 1 97 1 0 0 6228 18780 246036 167824 0 0 0 292 305 647 0 1 99 0 1 0 6228 18780 246036 167824 0 0 0 253 285 602 0 1 99 0 1 0 6228 18780 246036 167824 0 0 0 226 289 612 0 1 99 1 0 0 6228 18832 246036 167824 0 0 0 157 199 406 0 1 99 0 0 0 6228 18832 246036 167824 0 0 0 0 101 240 1 1 99 --- Another oddity -- If you add up the rates in the 2nd example, and multiply the average rate by 5, you get around 5200 blocks written out (for a 152M file). Note that a du on it shows it to use 155352, so it isn't that it is sparse. Is vmstat an unreliable measure? The above tests were on a 2216 system. -l -- L A Walsh | Trust Technology, Core Linux, SGI law@sgi.com | Voice/Vmail: (650) 933-5338 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/