[ovs-dev] [PATCH] Switch ovsdb log fsync to data only

[William Tu]

On Tue, Apr 21, 2020 at 09:23:57AM +0100, anton.ivanov at cambridgegreys.com wrote:
> From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
> 
> We do not check metadata - mtime, atime, anywhere, so we
> do not need to update it every time we sync the log.
> if the system supports it, the log update should be
> data only
> 
> Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
LGTM,
But how do you know we do not check mtime or atime of the ovsdb log file?
If there isn't a lot of performance overhead updating the metadata,
why not keep it as it is now?

William

> ---
>  ovsdb/log.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/ovsdb/log.c b/ovsdb/log.c
> index c82a79c9f..41af77679 100644
> --- a/ovsdb/log.c
> +++ b/ovsdb/log.c
> @@ -658,7 +658,16 @@ ovsdb_log_write_and_free(struct ovsdb_log *log, struct json *json)
>  struct ovsdb_error *
>  ovsdb_log_commit_block(struct ovsdb_log *file)
>  {
> +#if (_POSIX_C_SOURCE >= 199309L || _XOPEN_SOURCE >= 500)
> +    /* we do not check metadata - mtime, atime, anywhere, so we
> +     * do not need to update it every time we sync the log.
> +     * if the system supports it, the log update should be
> +     * data only
> +     */
> +    if (file->stream && fdatasync(fileno(file->stream))) {
> +#else
>      if (file->stream && fsync(fileno(file->stream))) {
> +#endif
>          return ovsdb_io_error(errno, "%s: fsync failed", file->display_name);
>      }
>      return NULL;
> -- 
> 2.20.1
> 
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