From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Gardner Subject: Re: Hi,something about the xentrace tool Date: Thu, 15 Jun 2006 12:53:14 -0600 Message-ID: <4491AC9A.2090906@hp.com> References: <8061f8830606150158m35f11025t43c3fa962ccd6679@mail.gmail.com> <449192E1.4080808@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: George Dunlap Cc: xen-tools@lists.xensource.com, xen-devel@lists.xensource.com, xen-users@lists.xensource.com, rickey berkeley List-Id: xen-devel@lists.xenproject.org George Dunlap wrote: > On 6/15/06, Rob Gardner wrote: >> I wouldn't call the amount of data 'huge'. Even on a very busy system, >> where there are thousands of trace records being generated every second, >> that's still a pretty small amount of data. (The size of a trace record >> is something like 50 or 60 bytes.) > > For the record, I think the trace record size in the trace buffers is > probably 32 bytes: You're right, I was thinking everything is 64 bits these days. In any case, it's a small amount of data. > If someone were really worried about copy time, one could write > something which uses raw disks (or, perhaps, the O_DIRECT flag) to DMA > data straight from the buffers to the disk. Once again, there is no explicit copying of the data between kernel and user space, so nobody should be worried about it. Rob