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Re: PostgreSQL performance issues

From: Willo van der Merwe <willo(at)studentvillage(dot)co(dot)za>
To: Dave Cramer <pg(at)fastcrypt(dot)com>
Cc: Luke Lonergan <LLonergan(at)greenplum(dot)com>,Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: PostgreSQL performance issues
Date: 2006-08-30 13:12:41
Message-ID: 44F58EC9.9090703@studentvillage.co.za (view raw or flat)
Thread:
Lists: pgsql-performance
Dave Cramer wrote:
>
> On 30-Aug-06, at 7:35 AM, Willo van der Merwe wrote:
>
>> Luke Lonergan wrote:
>>>> Currently the load looks like this:
>>>> Cpu0  : 96.8% us,  1.9% sy,  0.0% ni,  0.3% id,  0.0% wa,  0.0% 
>>>> hi,  1.0% si
>>>> Cpu1  : 97.8% us,  1.6% sy,  0.0% ni,  0.3% id,  0.0% wa,  0.0% 
>>>> hi,  0.3% si
>>>> Cpu2  : 96.8% us,  2.6% sy,  0.0% ni,  0.3% id,  0.0% wa,  0.0% 
>>>> hi,  0.3% si
>>>> Cpu3  : 96.2% us,  3.2% sy,  0.0% ni,  0.3% id,  0.0% wa,  0.0% 
>>>> hi,  0.3% si
>>>>
>>>
>>> All four CPUs are hammered busy - check "top" and look for runaway
>>> processes.
>>>
>>> - Luke
>>>
>>>
>>>
>> Yes, the first 463 process are all postgres. In the meanwhile I've done:
>> Dropped max_connections from 500 to 250 and
>> Upped shared_buffers = 50000
>
> With 4G of memory you can push shared buffers to double that.
> effective_cache should be 3/4 of available memory.
>
> Can you also check vmstat 1 for high context switches during this 
> query, high being over 100k
>
> Dave
>>
>> Without any apparent effect.
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 9: In versions below 8.0, the planner will ignore your desire to
>>       choose an index scan if your joining column's datatypes do not
>>       match
>>
>
>
Hi Dave,

Ok, I've upped shared_buffers = 150000
and effective_cache_size = 100000

and restarted the service
top now reads:

top - 15:08:28 up 20:12,  1 user,  load average: 19.55, 22.48, 26.59
Tasks: 132 total,  24 running, 108 sleeping,   0 stopped,   0 zombie
Cpu0  : 97.0% us,  1.0% sy,  0.0% ni,  0.3% id,  0.0% wa,  0.3% hi,  1.3% si
Cpu1  : 98.3% us,  1.7% sy,  0.0% ni,  0.0% id,  0.0% wa,  0.0% hi,  0.0% si
Cpu2  : 98.0% us,  1.7% sy,  0.0% ni,  0.0% id,  0.0% wa,  0.0% hi,  0.3% si
Cpu3  : 96.7% us,  3.3% sy,  0.0% ni,  0.0% id,  0.0% wa,  0.0% hi,  0.0% si
Mem:   4060084k total,  2661772k used,  1398312k free,   108152k buffers
Swap:  4192956k total,        0k used,  4192956k free,  2340936k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
11446 postgres  17   0 1280m  97m  95m R 28.9  2.5   0:03.63 postmaster
11435 postgres  16   0 1279m 120m 117m R 26.9  3.0   0:05.18 postmaster
11438 postgres  16   0 1279m  31m  30m R 24.6  0.8   0:04.43 postmaster
11163 postgres  16   0 1279m 120m 118m R 23.2  3.0   0:42.61 postmaster
11167 postgres  16   0 1279m 120m 118m R 23.2  3.0   0:41.04 postmaster
11415 postgres  15   0 1279m 299m 297m R 22.2  7.5   0:07.07 postmaster
11428 postgres  15   0 1279m  34m  32m R 21.9  0.9   0:05.53 postmaster
11225 postgres  16   0 1279m  31m  30m R 21.6  0.8   0:34.95 postmaster
11298 postgres  16   0 1279m 118m 117m R 21.6  3.0   0:23.82 postmaster
11401 postgres  15   0 1279m  31m  30m R 21.6  0.8   0:08.18 postmaster
11377 postgres  15   0 1279m 122m 120m R 20.9  3.1   0:09.54 postmaster
11357 postgres  17   0 1280m 126m 123m R 19.9  3.2   0:13.98 postmaster
11415 postgres  16   0 1279m 299m 297m R 17.1  7.5   0:06.40 postmaster
11461 postgres  17   0 1279m  81m  78m R 17.1  2.0   0:00.77 postmaster
11357 postgres  15   0 1279m 120m 118m S 16.8  3.0   0:13.38 postmaster
11458 postgres  16   0 1279m  31m  30m R 15.8  0.8   0:00.97 postmaster
11446 postgres  15   0 1279m  31m  30m S 15.5  0.8   0:02.76 postmaster
11428 postgres  15   0 1279m  34m  32m S 15.2  0.9   0:04.87 postmaster
11435 postgres  16   0 1279m 120m 117m R 14.2  3.0   0:04.37 postmaster
11466 postgres  16   0 1279m  33m  32m S  7.9  0.9   0:00.24 postmaster

load avg is climbing...

vmstat 1

I don't see any cs > 100k

procs -----------memory---------- ---swap-- -----io---- --system-- 
----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy 
id wa
33  0      0 1352128 108248 2352604    0    0     7    33  147    26 65  
2 33  0
19  0      0 1348360 108264 2352656    0    0     0   348 3588  1408 98  
2  0  0
26  0      0 1346024 108264 2352996    0    0     0    80 3461  1154 98  
2  0  0
27  0      0 1349496 108264 2352996    0    0     0   100 3611  1199 98  
2  0  0
31  0      0 1353872 108264 2353064    0    0     0   348 3329  1227 97  
2  0  0
21  0      0 1352528 108264 2353064    0    0     0    80 3201  1437 97  
2  0  0
28  0      0 1352096 108280 2353184    0    0     0    64 3579  1073 98  
2  0  0
29  0      0 1352096 108284 2353180    0    0     0     0 3538  1293 98  
2  0  0
28  0      0 1351776 108288 2353244    0    0     0    36 3339  1313 99  
1  0  0
22  0      0 1366392 108288 2353244    0    0     0   588 3663  1303 99  
1  0  0
27  0      0 1366392 108288 2353312    0    0     0    84 3276  1028 99  
1  0  0
28  0      0 1365504 108296 2353372    0    0     0   140 3500  1164 98  
2  0  0
26  0      0 1368272 108296 2353372    0    0     0    68 3268  1082 98  
2  0  0
25  0      0 1372232 108296 2353508    0    0     0   260 3261  1278 97  
3  0  0
26  0      0 1366056 108296 2353644    0    0     0     0 3268  1178 98  
2  0  0
24  1      0 1368704 108296 2353780    0    0     0  1788 3548  1614 97  
3  0  0
29  0      0 1367728 108296 2353304    0    0     0    60 3637  1105 99  
1  0  0
21  0      0 1365224 108300 2353640    0    0     0    12 3257   918 99  
1  0  0
27  0      0 1363944 108300 2354116    0    0     0    72 3052  1365 98  
2  0  0
25  0      0 1366968 108300 2354184    0    0     0   212 3314  1696 99  
1  0  0
30  0      0 1363552 108300 2354184    0    0     0    72 3147  1420 97  
2  0  0
27  0      0 1367792 108300 2354184    0    0     0   184 3245  1310 97  
2  0  0
21  0      0 1369088 108308 2354380    0    0     0   140 3306   987 98  
2  0  0
11  1      0 1366056 108308 2354448    0    0     0    88 3210  1183 98  
1  0  0
27  0      0 1361104 108308 2354516    0    0     0     0 3598  1015 98  
2  0  0
28  0      0 1356808 108308 2354584    0    0     0    64 2835  1326 98  
2  0  0
 3  0      0 1352888 108308 2354856    0    0     0    88 2829  1111 97  
3  0  0
29  0      0 1351408 108316 2354848    0    0     0   180 2916   939 97  
3  0  0
30  0      0 1352568 108316 2354848    0    0     0   112 2962  1122 98  
2  0  0
29  0      0 1356936 108316 2355052    0    0     0   176 2987   976 98  
2  0  0
27  0      0 1363816 108316 2355188    0    0     0   220 2990  1809 98  
2  0  0
24  0      0 1361944 108316 2355256    0    0     0     0 3043  1213 98  
2  0  0
24  0      0 1368808 108324 2355248    0    0     0   112 3168  1464 98  
2  0  0
24  0      0 1370120 108324 2355248    0    0     0   112 3179   997 99  
1  0  0
12  0      0 1370752 108324 2355248    0    0     0    16 3255  1081 97  
3  0  0
26  0      0 1372752 108324 2355248    0    0     0   112 3416  1169 98  
2  0  0
27  0      0 1369088 108324 2355248    0    0     0     0 3011   828 98  
2  0  0
20  0      0 1366848 108324 2355316    0    0     0    64 3062   959 98  
2  0  0
26  0      0 1368064 108328 2355312    0    0     0   264 3069  1064 97  
3  0  0
24  0      0 1365624 108328 2355448    0    0     0   152 2940  1344 98  
2  0  0
26  0      0 1363880 108328 2355584    0    0     0   128 3294  1122 98  
2  0  0
26  0      0 1370048 108328 2355652    0    0     0   152 3198  1340 97  
3  0  0
procs -----------memory---------- ---swap-- -----io---- --system-- 
----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy 
id wa
12  0      0 1369344 108328 2355720    0    0     0   184 2994  1030 98  
2  0  0


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Subject: Re: PostgreSQL performance issues
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