Hi, I can see two issues making you get variable results:
1/ Number of clients > scale factor
Using -c16 and -s 6 means you are largely benchmarking lock contention
for a row in the branches table (it has 6 rows in your case). So
randomness in *which* rows each client tries to lock will make for
unwanted variation.
2/ Short run times
That 1st run is 5s duration. This will be massively influenced by the
above point about randomness for locking a branches row.
I'd recommend:
- always run at least -T600
- use -s of at least 1.5x your largest -c setting (I usually use -s 100
for testing 1-32 clients).
regards
Mark
On 17/12/18 12:58 AM, Mariel Cherkassky wrote:
As Greg suggested, update you all that each vm has its own dedicated
esx. Every esx has it`s own local disks.
I run it one time on two different servers that has the same hardware
and same postgresql db (version and conf). The results :
pgbench -i -s 6 pgbench -p 5432 -U postgres
pgbench -c 16 -j 4 -T 5 -U postgres pgbench
MACHINE 1
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 6
query mode: simple
number of clients: 16
number of threads: 4
duration: 5 s
number of transactions actually processed: 669
latency average = 122.633 ms
tps = 130.470828 (including connections establishing)
tps = 130.620286 (excluding connections establishing)
MACHINE 2
pgbench -c 16 -j 4 -T 600 -U postgres -p 5433 pgbench
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 6
query mode: simple
number of clients: 16
number of threads: 4
duration: 600 s
number of transactions actually processed: 2393723
latency average = 4.011 ms
tps = 3989.437514 (including connections establishing)
tps = 3989.473036 (excluding connections establishing)
any idea what can cause such a difference ? Both of the machines have
20core and 65GB of ram.
בתאריך יום ה׳, 13 בדצמ׳ 2018 ב-15:54 מאת Mariel Cherkassky
<mariel.cherkassky@xxxxxxxxx <mailto:mariel.cherkassky@xxxxxxxxx>>:
Ok, I'll do that. Thanks .
בתאריך יום ה׳, 13 בדצמ׳ 2018 ב-15:54 מאת Greg Clough
<Greg.Clough@xxxxxxxxxxxxx <mailto:Greg.Clough@xxxxxxxxxxxxx>>:
Hmmm... sounds like you’ve got most of it covered. It may be
a good idea to send that last message back to the list, as
maybe others will have better ideas.
Greg.
*From:* Mariel Cherkassky <mariel.cherkassky@xxxxxxxxx
<mailto:mariel.cherkassky@xxxxxxxxx>>
*Sent:* Thursday, December 13, 2018 1:45 PM
*To:* Greg Clough <Greg.Clough@xxxxxxxxxxxxx
<mailto:Greg.Clough@xxxxxxxxxxxxx>>
*Subject:* Re: pgbench results arent accurate
Both of the machines are the only vms in a dedicated esx for
each one. Each esx has local disks.
On Thu, Dec 13, 2018, 3:05 PM Greg Clough
<Greg.Clough@xxxxxxxxxxxxx <mailto:Greg.Clough@xxxxxxxxxxxxx>
wrote:
> I installed a new postgres 9.6 on both of my machines.
Where is your storage? Is it local, or on a SAN? A SAN
will definitely have a cache, so possibly there is another
layer of cache that you’re not accounting for.
Greg Clough.
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