From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18631 invoked by alias); 6 Apr 2006 19:49:01 -0000 Received: (qmail 18596 invoked by alias); 6 Apr 2006 19:48:57 -0000 Date: Thu, 06 Apr 2006 19:49:00 -0000 Message-ID: <20060406194857.18595.qmail@sourceware.org> From: "hunt at redhat dot com" To: systemtap@sources.redhat.com In-Reply-To: <20060405143139.2514.guanglei@cn.ibm.com> References: <20060405143139.2514.guanglei@cn.ibm.com> Reply-To: sourceware-bugzilla@sourceware.org Subject: [Bug runtime/2514] Sequence had xxx drops. X-Bugzilla-Reason: AssignedTo Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2006-q2/txt/msg00057.txt.bz2 ------- Additional Comments From hunt at redhat dot com 2006-04-06 19:48 ------- Subject: Re: New: Sequence had xxx drops. On Wed, 2006-04-05 at 14:31 +0000, guanglei at cn dot ibm dot com wrote: > One reason I guess is that in such a heavy loaded system, the probe handlers are > triggered in a very high freq and generates too much data to be handled by > relayfs. The speed of putting into relayfs transport layer is much faster than > the speed that those data are retrieved away from relayfs from user space. > > So are there any ways of fixing this? It is a problem for the trace tool like > LKET which will generate a very large trace data file. The upper limit of both procfs and relayfs is the speed of the hard disks, typically around 40MB/sec. If you are trying to log more data than you can write to disk, you have a problem that cannot be fixed without upgrading your hardware. For bursts of data that temporarily exceed 40MB/sec, you can use "stap -s" to allocate a larger buffer size. It is possible to slow down the write process when the output buffer starts getting full to avoid dropped packets. I have experimented with this in procfs. However, that slows down the system and mainly just reduces the need for large buffers. It cannot increase the sustained logging rate which is limited by the drive speed. Martin -- http://sourceware.org/bugzilla/show_bug.cgi?id=2514 ------- You are receiving this mail because: ------- You are the assignee for the bug, or are watching the assignee.