digoal
2020-11-10
PostgreSQL , memory context , backenc pid
通过pg_backend_memory_contexts可查询任意backend pid的memory context, 为诊断提供更多有价值的参考信息.
https://www.postgresql.org/message-id/flat/0271f440ac77f2a4180e0e56ebd944d1@oss.nttdata.com
https://commitfest.postgresql.org/30/2711/
Get memory contexts of an arbitrary backend process
Hi,
After commit 3e98c0bafb28de, we can display the usage of the
memory contexts using pg_backend_memory_contexts system
view.
However, its target is limited to the process attached to
the current session.
As discussed in the thread[1], it'll be useful to make it
possible to get the memory contexts of an arbitrary backend
process.
Attached PoC patch makes pg_get_backend_memory_contexts()
display meory contexts of the specified PID of the process.
=# -- PID of the target process is 17051
=# SELECT * FROM pg_get_backend_memory_contexts(17051) ;
name | ident | parent | level |
total_bytes | total_nblocks | free_bytes | free_chunks | used_bytes
-----------------------+-------+------------------+-------+-------------+---------------+------------+-------------+------------
TopMemoryContext | | | 0 |
68720 | 5 | 16816 | 16 | 51904
RowDescriptionContext | | TopMemoryContext | 1 |
8192 | 1 | 6880 | 0 | 1312
MessageContext | | TopMemoryContext | 1 |
65536 | 4 | 19912 | 1 | 45624
...
It doesn't display contexts of all the backends but only
the contexts of specified process.
I think it would be enough because I suppose this function
is used after investigations using ps command or other OS
level utilities.
The rough idea of implementation is like below:
1. send a signal to the specified process
2. signaled process dumps its memory contexts to a file
3. read the dumped file and display it to the user
Any thoughts?
[1]
https://www.postgresql.org/message-id/72a656e0f71d0860161e0b3f67e4d771%40oss.nttdata.com
Regards,
--
Atsushi Torikoshi
NTT DATA CORPORATION
您的愿望将传达给PG kernel hacker、数据库厂商等, 帮助提高数据库产品质量和功能, 说不定下一个PG版本就有您提出的功能点. 针对非常好的提议，奖励限量版PG文化衫、纪念品、贴纸、PG热门书籍等，奖品丰富，快来许愿。开不开森.
