Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?

On Tue, Sep 20, 2022 at 04:00:26PM -0700, Nathan Bossart wrote:
> 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.

I also noticed that the latest patch set no longer applies, so I've marked
the commitfest entry as waiting-on-author.

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com