From: Tim Mohler (tamohler@nyc.rr.com)
Date: Tue Mar 04 2003 - 16:14:03 EST
Thanks to:
Kevin Buterbaugh
Chris Carrife
Joe Fletcher
for pointers.
Original question is appended below.
Chris recommended I try tying Postgres to 3 processors and see what
happened. Performance scaled down nearly linearly. I figured this took out
I/O bandwidth as an issue.
Kevin answered my question about interrupts - one CPU is handling the clock
interrupt, the other the I/O interrupts.
Joe Fletcher confirmed my feeling that the internal FC-AL drives on the V880
seem slow. I called Sun and they pointed me to a firmware upgrade for the
drives that does help.
Finally, though, I decided to play with the database - dropping the shared
buffer cache on Postgres by a factor of 9 (!!) nearly doubled performance.
Seems like its better to use the filesystem caching than Postgres? Any other
interpretations?
Thanks
Tim
-----Original Message-----
From: Tim Mohler [mailto:tamohler@nyc.rr.com]
Sent: Tuesday, February 25, 2003 4:25 PM
To: sunmanagers@sunmanagers.org
Subject: mpstat output - CPU contention or kernel thrashing?
Hi Managers -
Im running Solaris 9 on a 4-processor Sun-Fire V880 with 8GB of RAM. The
application is PostGres. We're topping out at around 260 transactions per
second (about 60% reads, 40% writes). My initial thought was that the system
was I/O bound, since the disk services times were excessive. Striping the
database boosted performance to current levels, but I'm still not satisfied.
Under a heavy load, mpstat gives output such as the following.
My questions - does the proportion of cross-calls indicate some sort of
kernel issue? Why are there two procesors with no ithr's running?
CPU minf mjf xcal intr ithr csw icsw migr smtx srw syscl usr sys wt idl
0 2938 78 3566 802 571 2417 405 383 175 10 4986 53 18 15 14
1 2675 91 2646 318 2 5801 3748 399 174 9 8784 57 13 17 13
2 2737 64 1704 341 0 2814 749 365 174 12 5471 51 14 23 12
3 2505 60 2212 1271 894 4009 2234 347 161 3 6272 52 21 10 17
CPU minf mjf xcal intr ithr csw icsw migr smtx srw syscl usr sys wt idl
0 1293 96 5238 1259 834 1931 672 222 84 0 5389 87 11 1 1
1 1241 111 3017 607 2 2335 868 229 82 0 7125 83 15 2 0
2 1484 113 2804 538 0 2043 657 243 75 0 5264 84 15 1 0
3 1285 102 3385 1857 1228 2249 808 245 88 0 5953 85 11 4 0
CPU minf mjf xcal intr ithr csw icsw migr smtx srw syscl usr sys wt idl
0 1009 113 5330 1189 766 1930 720 218 121 1 5676 80 15 4 1
1 1027 86 2635 545 2 3676 2342 221 155 1 9077 78 13 7 2
2 1208 102 2796 615 0 4173 2827 215 145 1 6820 80 14 5 1
3 939 98 2818 2027 1441 4904 3648 216 142 2 8028 77 19 4 0
CPU minf mjf xcal intr ithr csw icsw migr smtx srw syscl usr sys wt idl
0 934 102 5379 1332 783 2227 884 171 156 0 5640 79 21 0 0
1 959 116 3203 641 2 2380 964 201 141 0 8554 87 12 1 0
2 1038 106 3078 768 0 2558 1027 201 158 0 5951 86 14 0 0
3 881 96 3104 2302 1579 2185 871 181 135 0 4776 89 10 0 1
Thanks for any help,
Tim
_______________________________________________
sunmanagers mailing list
sunmanagers@sunmanagers.org
http://www.sunmanagers.org/mailman/listinfo/sunmanagers
This archive was generated by hypermail 2.1.7 : Wed Apr 09 2008 - 23:25:56 EDT