From: Nathan Bossart <nathandbossart@gmail.com>
To: pgsql-hackers@postgresql.org
Cc: andres@anarazel.de
Cc: noah@leadboat.com
Subject: Re: common signal handler protection
Date: Tue, 6 Feb 2024 20:39:41 -0600
Message-ID: <20240207023941.GA67817@nathanxps13> (raw)
In-Reply-To: <20231121212008.GA3742740@nathanxps13>
References: <20231121212008.GA3742740@nathanxps13>
On Tue, Nov 21, 2023 at 03:20:08PM -0600, Nathan Bossart wrote:
> * Overhead: The wrapper handler calls a function pointer and getpid(),
> which AFAICT is a real system call on most platforms. That might not be
> a tremendous amount of overhead, but it's not zero, either. I'm
> particularly worried about signal-heavy code like synchronous
> replication. (Are there other areas that should be tested?) If this is
> a concern, perhaps we could allow certain processes to opt out of this
> wrapper handler, provided we believe it is unlikely to fork or that the
> handler code is safe to run in grandchild processes.
I finally spent some time trying to measure this overhead. Specifically, I
sent many, many SIGUSR2 signals to postmaster, which just uses
dummy_handler(), i.e., does nothing. I was just barely able to get
wrapper_handler() to show up in the first page of 'perf top' in this
extreme case, which leads me to think that the overhead might not be a
problem.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, andres@anarazel.de, noah@leadboat.com
Subject: Re: common signal handler protection
In-Reply-To: <20240207023941.GA67817@nathanxps13>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox