From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
---|---|
To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
Cc: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: locked reads for atomics |
Date: | 2024-02-23 16:17:58 |
Message-ID: | 20240223161758.GA1697194@nathanxps13 |
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Lists: | pgsql-hackers |
On Thu, Feb 22, 2024 at 11:53:50AM -0800, Jeff Davis wrote:
> On Thu, 2024-02-22 at 12:58 +0530, Bharath Rupireddy wrote:
>> There's some immediate use for reads/writes with barrier semantics -
>
> Is this mainly a convenience for safety/readability? Or is it faster in
> some cases than doing an atomic access with separate memory barriers?
The former. Besides the 0002 patch tracked here, there's at least one
other patch [0] that could probably use these new functions. The idea is
to provide an easy way to remove spinlocks, etc. and use atomics for less
performance-sensitive stuff. The implementations are intended to be
relatively inexpensive and might continue to improve in the future, but the
functions are primarily meant to help reason about correctness.
I don't mind prioritizing these patches, especially since there now seems
to be multiple patches waiting on it. IIRC I was worried about not having
enough support for this change, but I might now have it.
[0] https://commitfest.postgresql.org/47/4330/
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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