grzaks's questions

I have two instances of PostgreSQL installed on my server: 8.3 and 9.0. There seams to be some problem with Polish diacritic characters (like ółęąśżźć) on postgresql 9.0 client - psql.

When I connect to DB (either 8.3 or 9.0) with psql 8.3 - I can type all diacritics on the terminal without any problems:

www:/tmp# sudo -u postgres /usr/lib/postgresql/8.3/bin/psql -q
postgres=# ółśćń

However, when I connect to the same DBs with psql 9.0 client - I can't type diacritics on the terminal anymore:

www:/tmp# sudo -u postgres /usr/lib/postgresql/8.3/bin/psql -q

Here are some encoding settings:

www:/tmp# sudo -u postgres /usr/lib/postgresql/9.0/bin/psql -q -c "show client_encoding"
 client_encoding
-----------------
 UTF8
(1 row)

.

www:/tmp# sudo -u postgres /usr/lib/postgresql/8.3/bin/psql -q -c "show client_encoding"
 client_encoding
-----------------
 UTF8
(1 row)

.

www:/tmp# sudo -u postgres /usr/lib/postgresql/9.0/bin/psql -q -l
                                         List of databases
        Name         |    Owner     | Encoding |  Collation  |    Ctype    |   Access privileges
---------------------+--------------+----------+-------------+-------------+-----------------------
 postgres            | postgres     | UTF8     | pl_PL.UTF-8 | pl_PL.UTF-8 |

.

www:/tmp# echo $LANG
pl_PL.UTF-8

It looks like DB/cluster configuration doesn't matter - if psql 8.x on terminal works fine and psql 9.x does not. Any idea how to fix that?

There is mod_setenv for adding:

setenv.add-response-header = ( "Header" => "value" )

But I can't find anything to remove response headers.

I have to be sure, that my content is not cached by mobile operator proxies. On Apache I was doing it with:

<Directory "/path/to/dir">
    Header set Cache-Control "no-cache, must-revalidate"
    Header add Pragma "no-cache"
    Header unset Last-Modified
    RequestHeader unset If-Modified-Since
</Directory>

How can I do that in lighttpd?

According to vmstat, my Linux server (2xCore2 Duo 2.5 GHz) is constantly doing around 20k context switches per second.

# vmstat 3
procs -----------memory----------  ---swap-- -----io----  -system-- ----cpu----
 r  b   swpd   free   buff  cache    si   so    bi    bo   in    cs us sy id wa
 2  0   7292 249472  82340 2291972    0    0     0     0    0     0  7 13 79  0
 0  0   7292 251808  82344 2291968    0    0     0   184   24 20090  1  1 99  0
 0  0   7292 251876  82344 2291968    0    0     0    83   17 20157  1  0 99  0
 0  0   7292 251876  82344 2291968    0    0     0    73   12 20116  1  0 99  0

... but uptime shows small load: load average: 0.01, 0.02, 0.01 and top doesn't show any process with high %CPU usage.

How do I find out what exactly is generating those context switches? Which process/thread?

I tried to analyze pidstat output:

# pidstat -w 10 1

12:39:13          PID   cswch/s nvcswch/s  Command
12:39:23            1      0.20      0.00  init
12:39:23            4      0.20      0.00  ksoftirqd/0
12:39:23            7      1.60      0.00  events/0
12:39:23            8      1.50      0.00  events/1
12:39:23           89      0.50      0.00  kblockd/0
12:39:23           90      0.30      0.00  kblockd/1
12:39:23          995      0.40      0.00  kirqd
12:39:23          997      0.60      0.00  kjournald
12:39:23         1146      0.20      0.00  svscan
12:39:23         2162      5.00      0.00  kjournald
12:39:23         2526      0.20      2.00  postgres
12:39:23         2530      1.00      0.30  postgres
12:39:23         2534      5.00      3.20  postgres
12:39:23         2536      1.40      1.70  postgres
12:39:23        12061     10.59      0.90  postgres
12:39:23        14442      1.50      2.20  postgres
12:39:23        15416      0.20      0.00  monitor
12:39:23        17289      0.10      0.00  syslogd
12:39:23        21776      0.40      0.30  postgres
12:39:23        23638      0.10      0.00  screen
12:39:23        25153      1.00      0.00  sshd
12:39:23        25185     86.61      0.00  daemon1
12:39:23        25190     12.19     35.86  postgres
12:39:23        25295      2.00      0.00  screen
12:39:23        25743      9.99      0.00  daemon2
12:39:23        25747      1.10      3.00  postgres
12:39:23        26968      5.09      0.80  postgres
12:39:23        26969      5.00      0.00  postgres
12:39:23        26970      1.10      0.20  postgres
12:39:23        26971     17.98      1.80  postgres
12:39:23        27607      0.90      0.40  postgres
12:39:23        29338      4.30      0.00  screen
12:39:23        31247      4.10     23.58  postgres
12:39:23        31249     82.92     34.77  postgres
12:39:23        31484      0.20      0.00  pdflush
12:39:23        32097      0.10      0.00  pidstat

Looks like some postgresql tasks are doing >10 context swiches per second, but it doesn't all sum up to 20k anyway.

Any idea how to dig a little deeper for an answer?