From: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes? |
Date: | 2023-02-13 04:45:03 |
Message-ID: | CALj2ACWjGYjaRg0Gt4nctRCup0XfNi1zfuQ2zpkbSkYm0LEJiQ@mail.gmail.com |
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Lists: | pgsql-hackers |
On Sun, Feb 12, 2023 at 11:01 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2023-02-12 19:59:00 +0530, Bharath Rupireddy wrote:
> > Thanks for looking at it. We know that we don't change the zbuffer in
> > the function, so can we avoid static const and have just a static
> > variable, like the attached
> > v1-0001-Use-static-variable-to-avoid-memset-calls-in-pg_p.patch? Do
> > you see any problem with it?
>
> Making it static const is better, because it allows the memory for the
> variable to be put in a readonly section.
Okay.
> > /* Prepare to write out a lot of copies of our zero buffer at once. */
> > for (i = 0; i < lengthof(iov); ++i)
> > {
> > - iov[i].iov_base = zbuffer.data;
> > + iov[i].iov_base = (void *) (unconstify(PGAlignedBlock *, &zbuffer)->data);
> > iov[i].iov_len = zbuffer_sz;
> > }
>
> Another thing: I think we should either avoid iterating over all the IOVs if
> we don't need them, or, even better, initialize the array as a constant, once.
How about like the attached patch? It makes the iovec static variable
and points the zero buffer only once/for the first time to iovec. This
avoids for-loop on every call.
--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
Attachment | Content-Type | Size |
---|---|---|
v1-0001-Optimize-zero-buffer-handling-in-pg_pwrite_zeros.patch | application/x-patch | 2.4 KB |
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