| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> |
| Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, 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: | 2022-09-20 23:00:26 |
| Message-ID: | 20220920230026.GA362217@nathanxps13 |
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| Lists: | pgsql-hackers |
On Mon, Aug 08, 2022 at 06:10:23PM +0530, Bharath Rupireddy wrote:
> I'm attaching v5 patch-set. I've addressed review comments received so
> far and fixed a compiler warning that CF bot complained about.
>
> Please review it further.
0001 looks reasonable to me.
+ errno = 0;
+ rc = pg_pwritev_zeros(fd, pad_to_size);
Do we need to reset errno? pg_pwritev_zeros() claims to set errno
appropriately.
+/*
+ * PWRITEV_BLCKSZ is same as XLOG_BLCKSZ for now, however it may change if
+ * writing more bytes per pg_pwritev_with_retry() call is proven to be more
+ * performant.
+ */
+#define PWRITEV_BLCKSZ XLOG_BLCKSZ
This seems like something we should sort out now instead of leaving as
future work. Given your recent note, I think we should just use
XLOG_BLCKSZ and PGAlignedXLogBlock and add a comment about the performance
findings with different buffer sizes.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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