From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Graham, Simon" Subject: RE: Reducing impact of save/restore/dump on Dom0 Date: Tue, 6 Feb 2007 12:46:52 -0500 Message-ID: <342BAC0A5467384983B586A6B0B3767104A69C19@EXNA.corp.stratus.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: Content-class: urn:content-classes:message List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Iustin Pop Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org > On linux, there is another way beside O_DIRECT: it's possible to reduce > the memory used for cached writing using the sysctl vm.dirty_ratio; > I've > used this to reduce the impact of heavy cached writes on dom0 with good > results. >=20 > Maybe it helps for save/dump also... Oh interesting -- I shall look into this.=20 I just took a quick peek and it is set to 40% in Dom0; I do see free memory go to zero during a dump (and save/restore) plus I see the waitIO% go to near 100% and Dom0 becomes somewhat unresponsive; specifically what we see is that domain boot fails during this time because of a XenBus timeout waiting for the hotplug scripts to finish adding the VBD in Dom0. I still feel that dump/save/restore files really don't belong in the system cache at all since they just pollute the cache for no ggood reason. Thanks, Simon