Re: IO on guest is 20 times slower than host

Kurt Yoder
2009-03-27T14:03:50Z

>> Kurt Yoder wrote:

<snip>

> me@guest:~# vmstat 1
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id
> wa
> 1 0 2616 686488 7756 208004 0 0 2 34 10 3 0 1 99
> 0
> 1 0 2616 680280 7764 213920 0 0 0 0 106 8 7 93 0
> 0
> 1 0 2616 674076 7768 219768 0 0 0 0 104 5 8 92 0
> 0
> 1 0 2616 669000 7780 224864 0 0 0 15124 188 14 1 99 0
> 0
> 1 0 2616 663168 7788 230700 0 0 0 0 104 5 4 96 0
> 0
> 1 0 2616 657836 7792 235472 0 0 0 5684 139 21 5 95 0
> 0
> 1 0 2616 651648 7796 241288 0 0 0 0 104 5 7 93 0
> 0
> 1 0 2616 645428 7804 247136 0 0 0 0 104 5 2 98 0
> 0
> 1 0 2616 640956 7816 251908 0 0 0 22164 232 31 3 97 0
> 0
> 1 0 2616 635016 7820 257732 0 0 0 0 104 5 2 98 0
> 0
> 1 0 2616 629204 7828 263552 0 0 0 0 105 9 2 98 0
> 0
> 1 0 2616 622732 7832 269392 0 0 0 0 104 5 5 95 0
> 0
> 1 0 2616 616676 7840 275096 0 0 0 0 104 7 5 95 0
> 0
> 1 0 2616 612200 7852 279540 0 0 0 27872 263 39 1 99 0
> 0
> 1 0 2616 606384 7856 285204 0 0 0 0 105 7 3 97 0
> 0
> 1 0 2616 600536 7860 290716 0 0 0 0 104 11 7 93 0
> 0
> 1 0 2616 594352 7868 296408 0 0 0 0 104 7 9 91 0
> 0

BTW, for comparison I did the same test on the other KVM host/guest, and
here is the vmstat -1:

me@otherhost:/etc/apache2# vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
3 0 55636 4520 956 37504 0 0 12 12 26 19 0 0 99 0
3 0 55636 3332 620 38516 0 0 0 81880 537 355 4 92 0 4
2 1 55636 3232 684 38508 0 0 8 56660 1708 550 2 97 0 1
2 1 55636 3200 764 38440 0 0 0 87696 409 271 4 96 0 0
2 1 55636 3096 852 38532 0 0 4 82824 394 254 4 95 0 1
3 1 55636 3072 848 38776 0 0 12 83520 429 293 8 91 0 1
3 1 55636 3204 536 38644 0 0 12 64856 1313 464 4 94 0 2
3 1 55636 3088 620 38484 192 0 280 85632 467 314 5 94 0 1
2 1 55636 3180 684 38428 0 0 0 67368 1011 443 3 97 0 0
2 1 55636 3080 768 38456 148 0 220 81432 414 270 8 91 0 1
3 0 55636 3124 784 38952 0 0 16 80416 554 284 5 94 0 1
3 1 55636 3004 488 38968 0 0 4 57756 1195 439 4 96 0 0
1 0 55636 4208 556 37644 0 0 4 75680 545 336 6 92 0 2
1 1 55636 3296 644 38388 0 0 0 87024 299 339 3 97 0 0
2 1 55636 2992 724 38648 0 0 4 78792 293 341 4 92 0 4
3 1 55636 3164 804 38660 0 0 8 73648 462 369 4 83 0 13
2 0 55636 2988 492 39044 0 0 8 73168 492 424 3 86 0 11

So clearly there is something odd going on with the first one. It looks
like it's CPU-bound, and this is throttling the IO?

-Kurt