From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (Postfix) with ESMTP id E7CCA7CBF for ; Wed, 12 Jun 2013 03:27:01 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay1.corp.sgi.com (Postfix) with ESMTP id C95FE8F8049 for ; Wed, 12 Jun 2013 01:26:58 -0700 (PDT) Received: from stockholm.opq.se ([213.88.151.150]) by cuda.sgi.com with ESMTP id zkpuQRw1R3pEiY3A (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Wed, 12 Jun 2013 01:26:56 -0700 (PDT) Received: from [10.2.10.35] (shark.pacific [10.2.10.35]) by stockholm.opq.se (8.13.4/8.13.4/SuSE Linux 0.7) with ESMTP id r5C8Qpu6027988 for ; Wed, 12 Jun 2013 10:26:53 +0200 Message-ID: <1371025611.7096.10.camel@acme> Subject: Re: Questions about XFS From: Roger Oberholtzer Date: Wed, 12 Jun 2013 10:26:51 +0200 In-Reply-To: References: <51B72D3D.5010206@redhat.com> Mime-Version: 1.0 List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com On Tue, 2013-06-11 at 11:12 -0500, Steve Bergman wrote: > Are you saying that with XFS there is no periodic > flushing mechanism at all? And that unless there's an > fsync/fdatasync/sync or the memory needs to be reclaimed, that it can > sit in the page cache forever? I read the later responses to this and they seemed to say that the data in the page cache should be written to the disk periodically. I am not meaning to hijack the thread. I just have a question directly related to this point. I have an application that is streaming data to an XFS disk at a sustained 25 MB/sec. This is well below what the hardware supports. The application does fopen/fwrite/fclose (no active flushing or syncing). I see that as my application writes data (the only process writing the only open file on the disk), the system cache grows and grows. Here is the unusual part: periodically, writes take some number of seconds to complete, rather than the typical <50 msecs). The increased time seems to correspond to the increasing size of the page cache. If I do: echo 1 > /proc/sys/vm/drop_caches while the application is runnung, then the writes do not occasionally take longer. Until the cache grows again, and I do the echo again. I am sure I must be misinterpreting what I see. (on openSUSE 12.1. kernel 3.1.0) -- Roger Oberholtzer _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs