[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] 4.2.1: Poor write performance for DomU.
Hi guys, Firstly, please CC me in to any replies as I'm not a subscriber these days.I've been trying to debug a problem with Xen 4.2.1 where I am unable to achieve more than ~50Mb/sec sustained sequential write to a disk. The DomU is configured as such: name = "zeus.vm" memory = 1024 vcpus = 2 cpus = "1-3"disk = [ 'phy:/dev/RAID1/zeus.vm,xvda,w', 'phy:/dev/vg_raid6/fileshare,xvdb,w' ] vif = [ "mac=02:16:36:35:35:09, bridge=br203, vifname=vm.zeus.203", "mac=10:16:36:35:35:09, bridge=br10, vifname=vm.zeus.10" ] bootloader = "pygrub" on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart'I have tested the underlying LVM config by mounting /dev/vg_raid6/fileshare from within the Dom0 and running bonnie++ as a benchmark: Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP xenhost.lan.crc. 2G 667 96 186976 21 80430 14 956 95 290591 26 373.7 8 Latency 26416us 212ms 168ms 35494us 35989us 83759usVersion 1.96 ------Sequential Create------ --------Random Create-------- xenhost.lan.crc.id. -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 14901 32 +++++ +++ 19672 39 15307 34 +++++ +++ 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 through as xvdb. It is then mounted in /mnt/fileshare/. I then ran bonnie++ again in the DomU: Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP zeus.crc.id.au 2G 658 96 50618 8 42398 10 1138 99 267568 30 494.9 11 Latency 22959us 226ms 311ms 14617us 41816us 72814usVersion 1.96 ------Sequential Create------ --------Random Create-------- zeus.crc.id.au -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 21749 59 +++++ +++ 31089 73 23283 64 +++++ +++ 31114 75 Latency 18989us 164us 928us 480us 26us 87us ~50Mb/sec write, ~267Mb/sec read. Not so awesome. /dev/vg_raid6/fileshare exists as an LV on /dev/md2: # lvdisplay vg_raid6/fileshare --- Logical volume --- LV Path /dev/vg_raid6/fileshare LV Name fileshare VG Name vg_raid6 LV UUID cwC0yK-Xr56-WB5v-10bw-3AZT-pYj0-piWett LV Write Access read/write LV Creation host, time xenhost.lan.crc.id.au, 2013-02-18 20:59:40 +1100 LV Status available # open 1 LV Size 2.50 TiB Current LE 655360 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 1024 Block device 253:5 md2 : active raid6 sdd[4] sdc[0] sde[1] sdf[5]3907026688 blocks super 1.2 level 6, 128k chunk, algorithm 2 [4/4] [UUUU] Heres a quick output of 'xm info' - although its full VM load is running now: # xm info host : xenhost.lan.crc.id.au release : 3.7.9-1.el6xen.x86_64 version : #1 SMP Mon Feb 18 14:46:35 EST 2013 machine : x86_64 nr_cpus : 4 nr_nodes : 1 cores_per_socket : 4 threads_per_core : 1 cpu_mhz : 3303hw_caps : bfebfbff:28100800:00000000:00003f40:179ae3bf:00000000:00000001:00000000 virt_caps : hvm total_memory : 8116 free_memory : 1346 free_cpus : 0 xen_major : 4 xen_minor : 2 xen_extra : .1xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64 xen_scheduler : credit xen_pagesize : 4096 platform_params : virt_start=0xffff800000000000 xen_changeset : unavailablexen_commandline : dom0_mem=1024M cpufreq=xen dom0_max_vcpus=1 dom0_vcpus_pin cc_compiler : gcc (GCC) 4.4.6 20120305 (Red Hat 4.4.6-4) cc_compile_by : mockbuild cc_compile_domain : crc.id.au cc_compile_date : Sat Feb 16 19:16:38 EST 2013 xend_config_format : 4In a nutshell, does anyone know *why* I am only able to get ~50Mb/sec sequential writes to the DomU? It certainly isn't a problem getting normal speeds to the LV while mounted in the Dom0. All OS are Scientific Linux 6.3. The Dom0 runs packages from my kernel-xen repo (http://au1.mirror.crc.id.au/repo/el6/x86_64/). The DomU is completely stock packages. -- Steven Haigh Email: netwiz@xxxxxxxxx Web: http://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897 Fax: (03) 8338 0299 Attachment:
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