Re: increasing the default WAL segment size

Hello all,

On Mon, Dec 19, 2016 at 3:14 PM, Beena Emerson <memissemerson(at)gmail(dot)com>
wrote:

> Hello all,
>
> Please find attached a patch to make wal segment size initdb configurable.
>
> The attached patch removes --with-wal-segsize configure option and adds a
> new initdb option --wal-segsize. The module initdb passes the wal-segsize
> value into an environment variable which is used to overwrite the guc value
> wal_ segment_size and set the internal variables : XLogSegSize and
> XLOG_SEG_SIZE (xlog_internal.h). The default wal_segment_size is not
> changed but I have increased the maximum size to 1GB.
>
> Since XLOG_SEG_SIZE is now variable, it could not be used directly in
> src/bin modules and few macros and few changes had to be made:
> - in guc.c , remove GUC_UNIT_XSEGS which used XLOG_SEG_SIZE and
> introduce show functions for the guc which used the unit (min_wal_size and
> max_wal_size).
> - For pg_basebackup, add new replication command SHOW_WAL_SEGSZ to
> fetch the wal_segment_size in bytes.
> - pg_controldata, pg_resetxlog, pg_rewind, fetch the xlog_seg_size from
> the ControlFile.
> - Since pg_xlogdump reads the wal files, it uses the file size to
> determine the xlog_seg_size.
> - In pg_test_fsync, a buffer of size XLOG_SEG_SIZE was created, filled
> with random data and written to a temporary file to check for any
> write/fsync error before performing the tests. Since it does not affect the
> actual performance results, the XLOG_SEG_SIZE in the module is replaced
> with the default value (16MB).
>
> Please note that the documents are not updated in this patch.
>
> Feedback and suggestions are welcome.
>

This patch has been added to the commit fest (https://commitfest.
postgresql.org/12/921/)

After further testing, I found that pg_standby contrib module does not work
with the changes. I will fix it in the next version of the patch. Comments
on the current patch are welcome.

Thank you,

Beena Emerson

Have a Great Day!