Seeing context switch storm with 10/13 snapshot of 8.1beta3

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От Robert Creager
Тема Seeing context switch storm with 10/13 snapshot of 8.1beta3
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Msg-id 20051013181243.000023cb@C118181.stortek.com
обсуждение исходный текст
Ответы Re: Seeing context switch storm with 10/13 snapshot of 8.1beta3  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
I've been having this problem since trying to upgrade from 7.4.1 to 8.03, and
now 8.1.

It's a dual Xenon machine:
Linux annette.stortek.com 2.4.22-26mdkenterprise #1 SMP Wed Jan 7 07:10:39 MST
2004 i686 unknown unknown GNU/Linux

PostgreSQL version is:
-------------------------------------------------------------------------------
----------------------------PostgreSQL 8.1beta3 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.3.1
(Mandrake Linux 9.2 3.3.1-2mdk)

[creagrs@annette creagrs]$ /usr/local/pgsql810/bin/pg_config
BINDIR = /usr/local/pgsql810/bin
DOCDIR = /usr/local/pgsql810/doc
INCLUDEDIR = /usr/local/pgsql810/include
PKGINCLUDEDIR = /usr/local/pgsql810/include
INCLUDEDIR-SERVER = /usr/local/pgsql810/include/server
LIBDIR = /usr/local/pgsql810/lib
PKGLIBDIR = /usr/local/pgsql810/lib
LOCALEDIR =
MANDIR = /usr/local/pgsql810/man
SHAREDIR = /usr/local/pgsql810/share
SYSCONFDIR = /usr/local/pgsql810/etc
PGXS = /usr/local/pgsql810/lib/pgxs/src/makefiles/pgxs.mk
CONFIGURE = '--enable-syslog' '--prefix=/usr/local/pgsql810' '--enable-debug'
CC = gcc
CPPFLAGS = -D_GNU_SOURCE
CFLAGS = -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Winline -Wendif-labels
-fno-strict-aliasing -g
CFLAGS_SL = -fpic
LDFLAGS = -Wl,-rpath,/usr/local/pgsql810/lib
LDFLAGS_SL =
LIBS = -lpgport -lz -lreadline -lncurses -lcrypt -lresolv -lnsl -ldl -lm -lbsd
VERSION = PostgreSQL 8.1beta3

I can reproduce this problem quite quickly with 20 concurrent queries (< 20
minutes with 5 sets of my app at 4 queries a piece, probably quicker).  The
queries nominally take < .1 second, but when all 5 sets run, the queries are up
around 5-6 seconds.  CS hit over 100k.  Below is a vmstat over a few seconds
which show the problem, then it subsides, then it hits again.  Note that when my
application gets up to 5 sets of 8, it never comes down again, and the queries
are over 40 seconds to complete.

When run against 7.4.1, the CS problem does not occur (stays < 10k).

[creagrs@annette creagrs]$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----r  b   swpd   free   buff  cache   si
so   bi    bo   in    cs us sy id wa
 
10  0   1032  63120     48 1608472    0    0     5    18    3     6 92  8  0  08  0   1032  62584     48 1608480    0
0     0    24  173 97793 39 61  0  09  0   1032  62332     48 1608500    0    0     0    32  197 83089 43 57  0  04  0
1032  61216     48 1608508    0    0     0    16  158 79967 43 57  0  06  0   1032  65208     48 1608556    0    0
0   88  262 91266 52 48  0  05  0   1032  67368     48 1608556    0    0     0   292  235 14234 87 13  0  04  0   1032
65780    48 1608580    0    0     0    40  173   325 95  5  0  04  0   1032  64764     48 1608580    0    0     0     0
144    86 98  2  0  06  0   1032  65800     48 1608580    0    0     0    24  197   397 96  4  0  06  0   1032  66284
 48 1608604    0    0     0    64  234  9284 83 17  0  06  0   1032  66104     48 1608604    0    0     0   116  253
8765856 44  0  05  0   1032  66276     48 1608612    0    0     0    56  245 20648 81 19  0  06  0   1032  65736     48
1608644   0    0     0    88  250 19699 82 18  0  05  0   1032  65316     48 1608652    0    0     0    40  215 73709
7030  0  05  0   1032  67664     48 1608700    0    0     0    96  272 22222 81 19  0  04  0   1032  66700     48
1608700   0    0     0    84  188   351 93  7  0  04  0   1032  67696     48 1608732    0    0     0    64  210   505
91 9  0  04  0   1032  67696     48 1608732    0    0     0     0  139    86 99  1  0  04  0   1032  64612     48
1608732   0    0     0     0  134    74 99  1  0  05  0   1032  65344     48 1608756    0    0     0    48  206   421
94 6  0  04  0   1032  66636     48 1608764    0    0     0    16  171   232 96  4  0  04  0   1032  67404     48
1608764   0    0     0     0  136    71 100  0  0  07  0   1032  63544     48 1608780    0    0     0    56  239 67250
6535  0  06  0   1032  65168     48 1608796    0    0     0    56  230 87782 59 41  0  07  0   1032  66588     48
1608820   0    0     0    72  236 106591 42 58  0  08  0   1032  62544     48 1608836    0    0     0   184  244 129696
4852  0  04  0   1032  63504     48 1608860    0    0     0    72  245 110887 48 52  0  08  0   1032  63400     48
1608868   0    0     0    16  156 101638 35 65  0  08  0   1032  62744     48 1608868    0    0     0    24  193 91159
4060  0  08  0   1032  63700     48 1608868    0    0     0    16  172 85165 42 58  0  07  0   1032  62888     48
1608876   0    0     0    48  228 94902 42 58  0  04  0   1032  64184     48 1608908    0    0     0    72  234 117585
4654  0  07  0   1032  61832     48 1608948    0    0     0    72  209 104287 46 54  0  08  0   1032  64468     48
1608956   0    0     0    56  237 112181 44 56  0  07  0   1032  63032     48 1608972    0    0     0    56  236 114977
4753  0  08  0   1032  63204     48 1608980    0    0     0    40  205 107433 45 55  0  07  0   1032  63832     48
1608996   0    0     0    56  225 113536 40 60  0  0
 

Help?

Thanks,
Rob

-- 
Robert Creager
Advisory Software Engineer
Data Management Group
Sun Microsystems
Robert.Creager@Sun.com
303.673.2365 Office
888.912.4458 Pager


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