From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tobias Geiger Subject: Re: Degregated I/O Performance since 3.4 - Regression in 3.4? Date: Mon, 23 Apr 2012 22:53:44 +0200 Message-ID: <4F95C158.7030703@vido.info> References: <201204231202.27731.tobias.geiger@vido.info> <20120423152404.GD24481@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120423152404.GD24481@phenom.dumpdata.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Konrad Rzeszutek Wilk Cc: "xen-devel@lists.xen.org" , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org Am 23.04.2012 17:24, schrieb Konrad Rzeszutek Wilk: > On Mon, Apr 23, 2012 at 12:53:03PM +0100, Stefano Stabellini wrote: >> On Mon, 23 Apr 2012, Tobias Geiger wrote: >>> Hello! >>> >>> i noticed a considerable drop in I/O Performance when using 3.4 (rc3 and rc4 >>> tested) as Dom0 Kernel; >>> >>> With 3.3 i get over 100mb/s in a HVM DomU (win64) with PV Drivers >>> (gplpv_Vista2008x64_0.11.0.357.msi); >>> With 3.4 it drops to about a third of that. >>> >>> Xen Version is xen-unstable: >>> xen_changeset : Tue Apr 17 19:13:52 2012 +0100 25209:e6b20ec1824c >>> >>> Disk config line is: >>> disk = [ '/dev/vg_ssd/win7system,,hda' ] >>> - it uses blkback. >> I fail to see what could be the cause of the issue: nothing on the >> blkback side should affect performances significantly. >> You could try reverting the four patches to blkback that were applied >> between 3.3 and 3.4-rc3 just to make sure it is not a blkback >> regression: >> >> $ git shortlog v3.3..v3.4-rc3 drivers/block/xen-blkback >> Daniel De Graaf (2): >> xen/blkback: use grant-table.c hypercall wrappers > Hm.. Perhaps this patch fixes it a possible perf (I would think that > the compiler would have kept the result of the first call to vaddr(req, i) > somewhere.. but not sure) lost with the mentioned patch: > > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c > index 73f196c..65dbadc 100644 > --- a/drivers/block/xen-blkback/blkback.c > +++ b/drivers/block/xen-blkback/blkback.c > @@ -327,13 +327,15 @@ static void xen_blkbk_unmap(struct pending_req *req) > int ret; > > for (i = 0; i< req->nr_pages; i++) { > + unsigned long addr; > handle = pending_handle(req, i); > if (handle == BLKBACK_INVALID_HANDLE) > continue; > - gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i), > + addr = vaddr(req, i); > + gnttab_set_unmap_op(&unmap[invcount], addr, > GNTMAP_host_map, handle); > pending_handle(req, i) = BLKBACK_INVALID_HANDLE; > - pages[invcount] = virt_to_page(vaddr(req, i)); > + pages[invcount] = virt_to_page(addr); > invcount++; > } > >> xen/blkback: Enable blkback on HVM guests >> >> Konrad Rzeszutek Wilk (2): >> xen/blkback: Squash the discard support for 'file' and 'phy' type. >> xen/blkback: Make optional features be really optional. >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xen.org >> http://lists.xen.org/xen-devel that made it even worse :) Write Performance is down to about 7mb/s (with 3.3: ~130mb/s) Read "only" down to 40mb/s (with 3.3: ~140mb/s) Greetings Tobias