| 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>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Subject: | Re: Improve WALRead() to suck data directly from WAL buffers when possible |
| Date: | 2023-10-25 01:54:01 |
| Message-ID: | 20231025015401.GB977906@nathanxps13 |
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| Lists: | pgsql-hackers |
On Tue, Oct 24, 2023 at 05:15:19PM -0700, Jeff Davis wrote:
> * Are you sure that reducing the number of calls to memcpy() is a win?
> I would expect that to be true only if the memcpy()s are tiny, but here
> they are around XLOG_BLCKSZ. I believe this was done based on a comment
> from Nathan Bossart, but I didn't really follow why that's important.
> Also, if we try to use one memcpy for all of the data, it might not
> interact well with my idea above to avoid taking the lock.
I don't recall exactly why I suggested this, but if additional memcpy()s
help in some way and don't negatively impact performance, then I retract my
previous comment.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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