public inbox for [email protected]  

help / color / mirror / Atom feed

From: Laurenz Albe <[email protected]>
To: James Pang <[email protected]>
To: [email protected]
Subject: Re: many sessions waiting DataFileRead and extend
Date: Wed, 25 Jun 2025 07:59:41 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAHgTRfdDkiX5bLRCYhrP18kFJjcvs1eHvL+jUtX1Ep-Y3=cFVg@mail.gmail.com>
References: <CAHgTRfdDkiX5bLRCYhrP18kFJjcvs1eHvL+jUtX1Ep-Y3=cFVg@mail.gmail.com>

On Wed, 2025-06-25 at 11:15 +0800, James Pang wrote:
> pgv14, RHEL8, xfs , we suddenly see tens of sessions waiting on "DataFileRead" and
> "extend", it last about 2 seconds(based on pg_stat_activity query) , during the
> waiting time, "%sys" cpu increased to 80% , but from "iostat" , no high iops and
> io read/write latency increased either.

Run "sar -P all 1" and see if "%iowait" is high.

Check if you have transparent hugepages enabled:

  cat /sys/kernel/mm/transparent_hugepage/enabled

If they are enabled, disable them and see if it makes a difference.

I am only guessing here.

> many sessions were running same "DELETE FROM xxxx" in parallel waiting on "extend"
> and "DataFileRead", there are triggers in this table "After delete" to insert/delete
> other tables in the tigger. 

One thing that almost certainly would improve your situation is to run fewer
concurrent statements, for example by using a reasonably sized connection pool.

Yours,
Laurenz Albe

view thread (14+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected]
  Subject: Re: many sessions waiting DataFileRead and extend
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox