From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: performance with guests running 2.4 kernels (specifically RHEL3) Date: Wed, 30 Apr 2008 16:49:55 +0300 Message-ID: <48187903.2070409@qumranet.com> References: <48054518.3000104@cisco.com> <4805BCF1.6040605@qumranet.com> <4807BD53.6020304@cisco.com> <48085485.3090205@qumranet.com> <480C188F.3020101@cisco.com> <480C5C39.4040300@qumranet.com> <480E492B.3060500@cisco.com> <480EEDA0.3080209@qumranet.com> <480F546C.2030608@cisco.com> <481215DE.3000302@cisco.com> <20080428181550.GA3965@dmt> <4816617F.3080403@cisco.com> <4817F30C.6050308@cisco.com> <48184228.2020701@qumranet.com> <481876A9.1010806@cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , Marcelo Tosatti To: "David S. Ahern" Return-path: In-Reply-To: <481876A9.1010806@cisco.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org David S. Ahern wrote: > Avi Kivity wrote: > >> David S. Ahern wrote: >> >>> Another tidbit for you guys as I make my way through various >>> permutations: >>> I installed the RHEL3 hugemem kernel and the guest behavior is *much* >>> better. >>> System time still has some regular hiccups that are higher than xen >>> and esx >>> (e.g., 1 minute samples out of 5 show system time between 10 and 15%), >>> but >>> overall guest behavior is good with the hugemem kernel. >>> >>> >>> >> Wait, the amount of info here is overwhelming. Let's stick with the >> current kernel (32-bit, HIGHMEM4G, right?) >> >> Did you get any traces with bypass_guest_pf=0? That may show more info. >> >> > > My preference is to stick with the "standard", 32-bit RHEL3 kernel in the guest. > Me too. I would like to see all reasonable guests supported well, without performance issues, and not have to tell the use which kernel to use. > My point in the last email was that the hugemem kernel shows a remarkable > difference (it uses 3-levels of page tables right?). I was hoping that would > ring a bell with someone. > From the traces I saw I think the standard kernel is pae as well. Can you verify? I think it's CONFIG_HIGHMEM4G (instead of CONFIG_HIGHMEM64G) but that option may be different for such an old kernel. > Adding bypass_guest_pf=0 did not improve the situation. Did you want anything > particular with that setting -- like a RIP summary or a summary of exit-entry > cycles? > I asked fo this thinking bypass_guest_pf may help show more information. But thinking a bit more, it will not. I think I do know what the problem is. I will try it out. Is there a free clone (like centos) available somewhere? -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone