When I run a certain large webserver benchmark, I prefer to warm the
pagecache up with the file set first, to cheat a little :) I grep
through 20 different 500MB file sets in parallel to do this. It is a
_lot_ slower in the BK snapshot than in plain 2.5.41.
And, no, these numbers aren't inflated, I have a lot of fast disks. I
_can_ do 50MB/sec :)
A little snipped from vmstat (I cut out the boring columns):
good kernel: 2.5.41: vmstat 4
Cached bi bo bi cs us s id
389280 53284 7 1625 3235 12 88 0
600580 53489 19 1599 3264 11 89 0
813428 53891 0 1587 3256 12 88 0
1027260 54093 0 1609 3239 12 88 0
1241448 54183 0 1611 3251 11 89 0
1454036 53790 0 1618 3267 12 88 0
doing the entire 10GB grep takes 192 seconds.
a dd produces: ~48000 bi/sec
exact same grep operation on kernel: 2.5.41+yesterday's bk: vmstat 4
Cached bi bo bi cs us sy id
4855948 9697 1 1408 846 20 80 0
4890464 8745 0 1398 800 18 82 0
4922392 8077 55 1364 676 21 79 0
4959164 9296 1 1399 798 18 82 0
4995936 9315 0 1407 830 19 81 0
5027208 7931 0 1351 638 22 78 0
5066256 9855 9 1416 856 19 81 0
I was too impatient to wait on the greps to complete.
a dd produces: ~37800 bi/sec
So, bi/sec goes from 54,000 in 2.5.41, to ~8700 in yesterday's
snapshot. It goes from around 50MB/sec to about 8MB/sec.
Although vmstat shows 0% idle time, the profilers show lots of idle
time, 98%! I tried oprofile and readprofile. Is the 2.0.9 vmstat
still broken? I'm using idle=poll if that makes any difference.
-- Dave Hansen haveblue@us.ibm.com- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Oct 15 2002 - 22:00:35 EST