----- Original Message ----- > From: "Tony Asleson" <tasle...@redhat.com> > To: vdsm-devel@lists.fedorahosted.org > Sent: Thursday, April 5, 2012 6:02:31 PM > Subject: Re: [vdsm] /etc/rc.c/init.d/vdsmd set filters for libvirt at DEBUG > level > > On 04/05/2012 03:42 PM, Saggi Mizrahi wrote: > > The performance implication though existing don't really pop up in > > normal use. > > In a previous life I worked on a product that logged a *ton* to > multiple > circular in memory binary buffers (memory was preserved on reset and > written to flash when the system booted to allow later retrieval aka. > flight recorder). It was optimized to minimize run-time costs (~10us > to > log a message). This was done so that you never had to re-create a > failure. No one believed that it would effect performance that much, > but one of the folks profiled it and found logging was eating at > least > 10% of the total CPU (embedded system).
Agreed. Nothing is for free, everything has a cost. > > It's true we usually don't need logs that far back but as I said > > it's > > really not an issue. Even when you try and run a 1000 VMs you will > > not be blocked on logging trying to get written to disk I can > > assure > > you of that. > > Has anyone gathered the data that shows what the logging costs when > you > have *many* VMs? Even a small operation can become relevant when you > have sufficiently large numbers of them. Working on that indirectly as we try to measure the time it takes to start up VMs using a vdsm client. > > -Tony > _______________________________________________ > vdsm-devel mailing list > vdsm-devel@lists.fedorahosted.org > https://fedorahosted.org/mailman/listinfo/vdsm-devel > _______________________________________________ vdsm-devel mailing list vdsm-devel@lists.fedorahosted.org https://fedorahosted.org/mailman/listinfo/vdsm-devel
