From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dr. Greg Wettstein" Subject: Re: [XenGT][IGVT-g] DomU pgt_device structure initialization Date: Thu, 21 Jan 2016 12:56:03 -0600 Message-ID: <201601211856.u0LIu3JU018177@wind.enjellic.com> References: Reply-To: greg@enjellic.com Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Oleksii Kurochko "Re: [Xen-devel] [XenGT][IGVT-g] DomU pgt_device structure initialization" (Jan 5, 10:04am) List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Oleksii Kurochko , "Tian, Kevin" Cc: "igvt-g@lists.01.org" , "Li, Susie" , "Dong, Eddie" , Gerd Hoffmann , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On Jan 5, 10:04am, Oleksii Kurochko wrote: } Subject: Re: [Xen-devel] [XenGT][IGVT-g] DomU pgt_device structure initial > Hey. Hi Oleksii, I hope this note finds your day going well. > Strange for me was that I got vmid=0 and gen_type=0, so I decided go > to i915_gem_vgtbuffer_ioctl and write next at the start: if > (!xen_initial_domain()) { return -EPERM; } Also same code is in 3.17 > kernel from XenGT-kernel repo. > > it seems that there is no more this error now( from vgt_fb_decoder ), BUT > there is often freeze or very laggy UI in guest. > > What it can be? It wasn't in this e-mail but I went through the console logs which were in one of your postings on the IGVT-g list. I believe you have your hypervisor configured for synchronous serial console output (sync_console command-line parameter) and you are directing your dom0 kernel console logging through the Xen provided serial interface. Setting this option is documented to cause significant latencies. In fact there is a warning about this in the Xen console logs when the hypervisor boots. Here is the code snippet from xen/drivers/char/console.c:console_endboot() which produces the message: if ( opt_sync_console ) { printk("**********************************************\n"); printk("******* WARNING: CONSOLE OUTPUT IS SYNCHRONOUS\n"); printk("******* This option is intended to aid debugging " "of Xen by ensuring\n"); printk("******* that all output is synchronously delivered " "on the serial line.\n"); printk("******* However it can introduce SIGNIFICANT latencies " "and affect\n"); printk("******* timekeeping. It is NOT recommended for " "production use!\n"); printk("**********************************************\n"); It appears as if you were generating significant amounts of kernel log output which may be at the root of the unacceptable latencies. I would start by turning off that option and see if your guest performance improves. > With best regards, > Oleksii Good luck with your work. Greg }-- End of excerpt from Oleksii Kurochko As always, Dr. G.W. Wettstein, Ph.D. Enjellic Systems Development, LLC. 4206 N. 19th Ave. Specializing in information infra-structure Fargo, ND 58102 development. PH: 701-281-1686 FAX: 701-281-3949 EMAIL: greg@enjellic.com ------------------------------------------------------------------------------ "Sweeny's Law: The length of a progress report is inversely proportional to the amount of progress." --