Hi there,
I see a very low performance and high context switches on our
dual itanium2 slackware box (Linux ptah 2.6.14 #1 SMP)
with 8Gb of RAM, running 8.1_STABLE. Any tips here ?
postgres@ptah:~/cvs/8.1/pgsql/contrib/pgbench$ time pgbench -s 10 -c
10 -t 3000 pgbench
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
number of clients: 10
number of transactions per client: 3000
number of transactions actually processed: 30000/30000
tps = 163.817425 (including connections establishing)
tps = 163.830558 (excluding connections establishing)
real 3m3.374s
user 0m1.888s
sys 0m2.472s
output from vmstat 2
2 1 0 4185104 197904 3213888 0 0 0 1456 673 6852
25 1 45 29
6 0 0 4184880 197904 3213888 0 0 0 1456 673 6317
28 2 49 21
0 1 0 4184656 197904 3213888 0 0 0 1464 671 7049
25 2 42 31
3 0 0 4184432 197904 3213888 0 0 0 1436 671 7073
25 1 44 29
0 1 0 4184432 197904 3213888 0 0 0 1460 671 7014
28 1 42 29
0 1 0 4184096 197920 3213872 0 0 0 1440 670 7065
25 2 42 31
0 1 0 4183872 197920 3213872 0 0 0 1444 671 6718
26 2 44 28
0 1 0 4183648 197920 3213872 0 0 0 1468 670 6525
15 3 50 33
0 1 0 4184352 197920 3213872 0 0 0 1584 676 6476
12 2 50 36
0 1 0 4193232 197920 3213872 0 0 0 1424 671 5848
12 1 50 37
0 0 0 4195536 197920 3213872 0 0 0 20 509 104
0 0 99 1
0 0 0 4195536 197920 3213872 0 0 0 1680 573 25
0 0 99 1
0 0 0 4195536 197920 3213872 0 0 0 0 504 22
0 0 100
processor : 1
vendor : GenuineIntel
arch : IA-64
family : Itanium 2
model : 2
revision : 2
archrev : 0
features : branchlong
cpu number : 0
cpu regs : 4
cpu MHz : 1600.010490
itc MHz : 1600.010490
BogoMIPS : 2392.06
siblings : 1
On Mon, 19 Dec 2005, Anjan Dave wrote:
Re-ran it 3 times on each host -
Sun:
-bash-3.00$ time pgbench -s 10 -c 10 -t 3000 pgbench
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
number of clients: 10
number of transactions per client: 3000
number of transactions actually processed: 30000/30000
tps = 827.810778 (including connections establishing)
tps = 828.410801 (excluding connections establishing)
real 0m36.579s
user 0m1.222s
sys 0m3.422s
Intel:
-bash-3.00$ time pgbench -s 10 -c 10 -t 3000 pgbench
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 1
number of clients: 10
number of transactions per client: 3000
number of transactions actually processed: 30000/30000
tps = 597.067503 (including connections establishing)
tps = 597.606169 (excluding connections establishing)
real 0m50.380s
user 0m2.621s
sys 0m7.818s
Thanks,
Anjan
-----Original Message-----
From: Anjan Dave
Sent: Wed 12/7/2005 10:54 AM
To: Tom Lane
Cc: Vivek Khera; Postgresql Performance
Subject: Re: [PERFORM] High context switches occurring
Thanks for your inputs, Tom. I was going after high concurrent
clients,
but should have read this carefully -
-s scaling_factor
this should be used with -i (initialize) option.
number of tuples generated will be multiple of the
scaling factor. For example, -s 100 will imply 10M
(10,000,000) tuples in the accounts table.
default is 1. NOTE: scaling factor should be at
least
as large as the largest number of clients you intend
to test; else you'll mostly be measuring update
contention.
I'll rerun the tests.
Thanks,
Anjan
-----Original Message-----
From: Tom Lane [mailto:tgl@xxxxxxxxxxxxx]
Sent: Tuesday, December 06, 2005 6:45 PM
To: Anjan Dave
Cc: Vivek Khera; Postgresql Performance
Subject: Re: [PERFORM] High context switches occurring
"Anjan Dave" <adave@xxxxxxxxxxx> writes:
> -bash-3.00$ time pgbench -c 1000 -t 30 pgbench
> starting vacuum...end.
> transaction type: TPC-B (sort of)
> scaling factor: 1
> number of clients: 1000
> number of transactions per client: 30
> number of transactions actually processed: 30000/30000
> tps = 45.871234 (including connections establishing)
> tps = 46.092629 (excluding connections establishing)
I can hardly think of a worse way to run pgbench :-(. These
numbers are
about meaningless, for two reasons:
1. You don't want number of clients (-c) much higher than scaling
factor
(-s in the initialization step). The number of rows in the
"branches"
table will equal -s, and since every transaction updates one
randomly-chosen "branches" row, you will be measuring mostly
row-update
contention overhead if there's more concurrent transactions than
there
are rows. In the case -s 1, which is what you've got here, there
is no
actual concurrency at all --- all the transactions stack up on the
single branches row.
2. Running a small number of transactions per client means that
startup/shutdown transients overwhelm the steady-state data. You
should
probably run at least a thousand transactions per client if you want
repeatable numbers.
Try something like "-s 10 -c 10 -t 3000" to get numbers
reflecting test
conditions more like what the TPC council had in mind when they
designed
this benchmark. I tend to repeat such a test 3 times to see if the
numbers are repeatable, and quote the middle TPS number as long as
they're not too far apart.
regards, tom lane
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_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@xxxxxxxxxx, http://www.sai.msu.su/~megera/
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