Re: Swap on postgres master server

No it is not probably used, because I can't find it in any way as I said.

I run your commands :

[root(at)usnyh-cmd1 ~]# vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system--
------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id
wa st
3 2 7505332 14545468 13692 241436784 0 0 47 115 0 0 11
2 84 2 0
3 2 7505332 14490408 13692 241436928 0 0 0 248 6153 2013 3
1 93 3 0
1 2 7505332 14474672 13692 241436800 0 0 0 1124 4905 1454 3
1 93 3 0
4 2 7505332 14381156 13692 241436832 0 0 0 96 5322 1782 2
1 94 3 0
^C
[root(at)usnyh-cmd1 ~]# ps -A --sort -rss -o comm,pmem | awk '
> NR == 1 { print; next }
> { a[$1] += $2 }
> END {
> for (i in a) {
> printf "%-15s\t%s\n", i, a[i];
> }
> }
> '
COMMAND %MEM
kworker/42:2 0
kworker/60:6H 0
kworker/60:2H 0
kdmwork-253:2 0
ksoftirqd/60 0
postmaster 15.2
kworker/9:0H 0

So I'm just asking why it is still there with free -m and if there is any
way to free that up if it is not used.

Thanks

Il giorno mar 16 ott 2018 alle ore 11:18 Hans Schou <hans(dot)schou(at)gmail(dot)com>
ha scritto:

> Are you sure that swap is used actively? Maybe it had just been used
> during backup or something.
>
> Look after SwapIn/SwapOut (si/so) it should be '0'
> $ vmstat 1
> procs -----------memory---------- ---swap-- -----io---- -system--
> ------cpu-----
> r b swpd free buff cache si so bi bo in cs us sy id
> wa st
> 1 0 12 89344 46608 586384 0 0 12 8 30 86 0 0
> 99 0 0
>
> If you want to see the amount of ram used by each program with childs run
> this:
> ps -A --sort -rss -o comm,pmem | awk '
> NR == 1 { print; next }
> { a[$1] += $2 }
> END {
> for (i in a) {
> printf "%-15s\t%s\n", i, a[i];
> }
> }
> '
>
>
> On Tue, Oct 16, 2018 at 11:04 AM Nicola Contu <nicola(dot)contu(at)gmail(dot)com>
> wrote:
>
>> Hello,
>> we are running Postgres 10.5 with master slave replication.
>>
>> These are our custom params
>>
>> archive_command = 'pgbackrest --stanza=cmdprod archive-push %p' #
>> command to use to archive a logfile segment
>> archive_mode = on # enables archiving; off, on, or always
>> checkpoint_completion_target = 0.7 # checkpoint target duration, 0.0 -
>> 1.0
>> default_text_search_config = 'pg_catalog.english' #
>> datestyle = 'iso, mdy' #
>> effective_cache_size = 120GB #
>> hot_standby = on # "on" allows queries during
>> recovery
>> lc_messages = 'en_US.UTF-8' # locale for system
>> error message
>> lc_monetary = 'en_US.UTF-8' # locale for monetary
>> formatting
>> lc_numeric = 'en_US.UTF-8' # locale for number
>> formatting
>> lc_time = 'en_US.UTF-8' # locale for time
>> formatting
>> listen_addresses = '*' # defaults to 'localhost', '*' = all
>> log_autovacuum_min_duration = 1000ms # -1 disables, 0 logs all
>> actions and
>> log_checkpoints = on #
>> log_line_prefix = '%t [%r] [%p]: [%l-1] db=%d,user=%u ' #
>> log_lock_waits = on # log lock waits >=
>> deadlock_timeout
>> log_min_duration_statement = 1000ms # -1 is disabled, 0 logs all
>> statements
>> log_statement = 'ddl' # none, ddl, mod, all
>> log_temp_files = 1024kB # log temporary files equal
>> or larger
>> maintenance_work_mem = 2GB #
>> max_connections = 220 #
>> max_parallel_workers_per_gather = 8 # taken from
>> max_worker_processes
>> max_wal_size = 2GB #
>> min_wal_size = 1GB #
>> pg_stat_statements.max = 10000 #
>> pg_stat_statements.track = all #
>> port = 5432 # port number which Postgres
>> listen
>> shared_buffers = 10GB #
>> shared_preload_libraries = 'pg_stat_statements' # (change
>> requires restart)
>> synchronous_standby_names = '1 ( "usnyh2" )' # comment out during upgrade
>> track_activity_query_size = 16384 # (change requires restart)
>> track_io_timing = on #
>> wal_buffers = 16MB #
>> wal_keep_segments = 100 #
>> wal_level = replica # minimal, replica, or logical
>> work_mem = 600MB #
>>
>> This server is on Centos 7 and the strange thing is that we see a lot of
>> swap usage :
>>
>> [root(at)usnyh-cmd1 ~]# free -m
>> total used free shared buff/cache
>> available
>> Mem: 257652 7555 5559 12804 244536
>> 236036
>> Swap: 16383 7326 9057
>>
>> 7GB used.
>>
>> But can't see it from any of the commands like top etc.
>> I am sure it is postgres because it is the only service running on that
>> machine.
>>
>> Is there anything we can do?
>> On the sync slave, the usage is just 400MB.
>>
>> Any trick?
>>
>> Thanks a lot,
>> Nicola
>>
>