From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Haigh Subject: Re: 4.2.1: Poor write performance for DomU. Date: Sat, 09 Mar 2013 09:30:54 +1100 Message-ID: <513A669E.4060906@crc.id.au> References: <51243089.8020307@crc.id.au> <512488AC.1020702@citrix.com> <51248E23.7060408@crc.id.au> <51249C11.3050800@crc.id.au> <5139A747.80703@crc.id.au> <20130308204916.GB22146@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1354119515013228511==" Return-path: In-Reply-To: <20130308204916.GB22146@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: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org This is a cryptographically signed message in MIME format. --===============1354119515013228511== Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms010108060604060900020706" This is a cryptographically signed message in MIME format. --------------ms010108060604060900020706 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable On 9/03/2013 7:49 AM, Konrad Rzeszutek Wilk wrote: > On Fri, Mar 08, 2013 at 07:54:31PM +1100, Steven Haigh wrote: >> On 20/02/2013 8:49 PM, Steven Haigh wrote: >>> On 20/02/2013 7:49 PM, Steven Haigh wrote: >>>> On 20/02/2013 7:26 PM, Roger Pau Monn=E9 wrote: >>>>> On 20/02/13 03:10, Steven Haigh wrote: >>>>>> Hi guys, >>>>>> >>>>>> Firstly, please CC me in to any replies as I'm not a subscriber th= ese >>>>>> days. >>>>>> >>>>>> I've been trying to debug a problem with Xen 4.2.1 where I am unab= le to >>>>>> achieve more than ~50Mb/sec sustained sequential write to a disk. = The >>>>>> DomU is configured as such: >>>>> >>>>> Since you mention 4.2.1 explicitly, is this a performance regressio= n >>>> >from previous versions? (4.2.0 or the 4.1 branch) >>>> >>>> This is actually a very good question. I've reinstalled my older >>>> packages of Xen 4.1.3 back on the system. Rebooting into the new >>>> hypervisor, then starting the single DomU again. Ran bonnie++ again = on >>>> the DomU: >>>> >>>> Still around 50Mb/sec - so this doesn't seem to be a regression, but= >>>> something else? >>> >>> I've actually done a bit of thinking about this... A recent thread on= >>> linux-raid kernel mailing list about Xen and DomU throughput made me >>> revisit my setup. I know I used to be able to saturate GigE both ways= >>> (send and receive) to the samba share served by this DomU. This would= >>> mean I'd get at least 90-100Mbyte/sec. What exact config and kernel/x= en >>> versions this was as this point in time I cannot say. >>> >>> As such, I had a bit of a play and recreated my RAID6 with 64Kb chunk= >>> size. This seemed to make rebuild/resync speeds way worse - so I >>> reverted to 128Kb chunk size. >>> >>> The benchmarks I am getting from the Dom0 is about what I'd expect - = but >>> I wouldn't expect to lose 130Mb/sec write speed to the phy:/ pass >>> through of the LV. >>> >>> From my known config where I could saturate the GigE connection, I h= ave >>> changed from kernel 2.6.32 (Jeremy's git repo) to the latest vanilla >>> kernels - currently 3.7.9. >>> >>> My build of Xen 4.2.1 also has all of the recent security advisories >>> patched as well. Although it is interesting to note that downgrading = to >>> Xen 4.1.2 made no difference to write speeds. >>> >> >> Just wondering if there is any further news or tests that I might be >> able to do on this? > > So usually the problem like this is to unpeel the layers and find out > which of them is at fault. You have a stacked block system - LVM on > top of RAID6 on top of block devices. > > To figure out who is interferring with the speeds I would recommend > you fault one of the RAID6 disks (so take it out of the RAID6). Pass > it to the guest as a raw disk (/dev/sdX as /dev/xvd) and then > run 'fio'. Run 'fio' as well in dom0 on the /dev/sdX and check > whether the write performance is different. > > This is how I how do it: > > [/dev/xvdXXX] > rw=3Dwrite > direct=3D1 > size=3D4g > ioengine=3Dlibaio > iodepth=3D32 > > Then progress up the stack. Try sticking the disk back in RAID6 > and doing it on the RAID6. Then on the LVM and so on. I did try to peel it back a single layer at a time. My test was simply=20 using the same XFS filesystem in the Dom0 instead of the DomU. I tested the underlying LVM config by mounting /dev/vg_raid6/fileshare=20 from within the Dom0 and running bonnie++ as a benchmark: Version 1.96 ------Sequential Output------ --Sequential Input-=20 --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--=20 --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP=20 /sec %CP xenhost.lan.crc. 2G 667 96 186976 21 80430 14 956 95 290591 26=20 373.7 8 Latency 26416us 212ms 168ms 35494us 35989us 83759= us Version 1.96 ------Sequential Create------ --------Random=20 Create-------- xenhost.lan.crc.id. -Create-- --Read--- -Delete-- -Create-- --Read---=20 -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP=20 /sec %CP 16 14901 32 +++++ +++ 19672 39 15307 34 +++++ +++=20 18158 37 Latency 17838us 141us 298us 365us 133us 296us= ~186Mb/sec write, ~290Mb/sec read. Awesome. I then started a single DomU which gets passed /dev/vg_raid6/fileshare=20 through as xvdb. It is then mounted in /mnt/fileshare/. I then ran=20 bonnie++ again in the DomU: Version 1.96 ------Sequential Output------ --Sequential Input-=20 --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--=20 --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP=20 /sec %CP zeus.crc.id.au 2G 658 96 50618 8 42398 10 1138 99 267568 30=20 494.9 11 Latency 22959us 226ms 311ms 14617us 41816us 72814= us Version 1.96 ------Sequential Create------ --------Random=20 Create-------- zeus.crc.id.au -Create-- --Read--- -Delete-- -Create-- --Read---=20 -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP=20 /sec %CP 16 21749 59 +++++ +++ 31089 73 23283 64 +++++ +++=20 31114 75 Latency 18989us 164us 928us 480us 26us 87us= ~50Mb/sec write, ~267Mb/sec read. Not so awesome. As such, the filesystem, RAID6, etc are completely unchanged. The only=20 change is the access method Dom0 vs DomU. --=20 Steven Haigh Email: netwiz@crc.id.au Web: https://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897 Fax: (03) 8338 0299 --------------ms010108060604060900020706 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIMdTCC BjQwggQcoAMCAQICAR4wDQYJKoZIhvcNAQEFBQAwfTELMAkGA1UEBhMCSUwxFjAUBgNVBAoT DVN0YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNp Z25pbmcxKTAnBgNVBAMTIFN0YXJ0Q29tIENlcnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA3 MTAyNDIxMDE1NVoXDTE3MTAyNDIxMDE1NVowgYwxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1T dGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0aWZpY2F0ZSBTaWdu aW5nMTgwNgYDVQQDEy9TdGFydENvbSBDbGFzcyAxIFByaW1hcnkgSW50ZXJtZWRpYXRlIENs 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