On 01/07/14 23:25, Heikki Linnakangas wrote:
On 07/01/2014 01:08 PM, Andres Freund wrote:
Hi,
Over at -performance Mark Kirkwood tested a recent version of this
(http://archives.postgresql.org/message-id/53B283F3.7020005%40catalyst.net.nz)
. I thought it's interesting to add the numbers to this thread:
Test: pgbench
Options: scale 500
read only
Os: Ubuntu 14.04
Pg: 9.3.4
Pg Options:
max_connections = 200
shared_buffers = 10GB
maintenance_work_mem = 1GB
effective_io_concurrency = 10
wal_buffers = 32MB
checkpoint_segments = 192
checkpoint_completion_target = 0.8
Results
Clients | 9.3 tps 32 cores | 9.3 tps 60 cores
--------+------------------+-----------------
6 | 70400 | 71028
12 | 98918 | 129140
24 | 230345 | 240631
48 | 324042 | 409510
96 | 346929 | 120464
192 | 312621 | 92663
So we have anti scaling with 60 cores as we increase the client
connections.
Ouch! A level of urgency led to trying out Andres's 'rwlock' 9.4
branch [1]
- cherry picking the last 5 commits into 9.4 branch and building a
package
from that and retesting:
Clients | 9.4 tps 60 cores (rwlock)
--------+--------------------------
6 | 70189
12 | 128894
24 | 233542
48 | 422754
96 | 590796
192 | 630672
Now, this is a bit of a skewed comparison due to 9.4 vs. 9.3 but still
interesting.
It looks like the issue I reported here:
http://www.postgresql.org/message-id/5190e17b.9060...@vmware.com
fixed by this commit:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=b03d196be055450c7260749f17347c2d066b4254.
So, definitely need to compare plain 9.4 vs patched 9.4, not 9.3.
Here's plain 9.4 vs patched 9.4:
Clients | 9.4 tps 60 cores | 9.4 tps 60 cores (rwlock)
--------+------------------+--------------------------
6 | 69490 | 70189
12 | 128200 | 128894
24 | 232243 | 233542
48 | 417689 | 422754
96 | 464037 | 590796
192 | 418252 | 630672
It appears that plain 9.4 does not exhibit the dramatic anti scaling
that 9.3 showed, but there is still evidence of some contention in the
higher client numbers, and we peak at the 96 client mark. The patched
variant looks pretty much free from this, still scaling at 192
connections (might have been interesting to try more, but had
max_connections set to 200)!
Cheers
Mark
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