maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxxx>]

Hi, Vladislav!

On Mar 29, Vladislav Vaintroub wrote:
> ------------------------------------------------------------
> revno: 3712
> revision-id: wlad@xxxxxxxxxxxxxxxx-20130328203348-1qe9u9nlq6ol9b8l
> parent: igor@xxxxxxxxxxxx-20130329021836-x6swah73a59im9tn
> fixes bug: https://mariadb.atlassian.net/browse/MDEV-4338
> committer: Vladislav Vaintroub <wlad@xxxxxxxxxxxxxxxx>
> branch nick: 5.5
> timestamp: Thu 2013-03-28 21:33:48 +0100
> message:
>   MDEV-4338 : Support atomic option on directFS/FusionIO.

> === modified file 'storage/xtradb/handler/ha_innodb.cc'
> --- a/storage/xtradb/handler/ha_innodb.cc	2013-03-08 18:08:45 +0000
> +++ b/storage/xtradb/handler/ha_innodb.cc	2013-03-28 20:33:48 +0000
> @@ -185,6 +185,7 @@ static my_bool	innobase_file_format_chec
>  static my_bool  innobase_log_archive                    = FALSE;
>  static char*    innobase_log_arch_dir                   = NULL;
>  #endif /* UNIV_LOG_ARCHIVE */
> +static my_bool  innobase_use_atomic_writes              = TRUE;
>  static my_bool  innobase_use_doublewrite                = TRUE;
>  static my_bool  innobase_use_checksums                  = TRUE;
>  static my_bool  innobase_fast_checksum                  = FALSE;
> @@ -3057,6 +3058,35 @@ innobase_init(
>          srv_kill_idle_transaction = 0;
>  #endif
>  
> +        srv_use_atomic_writes = (ibool) innobase_use_atomic_writes;

Is that the typical usage pattern in the innodb code?
Because it looks a bit silly to me, why couldn't you create a sysvar
directly on srv_use_atomic_writes, why an intermediate
innobase_use_atomic_writes variable?

> +        if (innobase_use_atomic_writes) {
> +                fprintf(stderr, "InnoDB: using atomic writes.\n");
> +
> +                /* Force doublewrite buffer off, atomic writes replace it. */
> +                if (srv_use_doublewrite_buf) {
> +                        fprintf(stderr, "InnoDB: Switching off doublewrite buffer "
> +                                "because of atomic writes.\n");
> +                                innobase_use_doublewrite = srv_use_doublewrite_buf = FALSE;
> +                }
> +
> +                /* Force O_DIRECT on Unixes (on Windows writes are always unbuffered)*/
> +#ifndef _WIN32
> +                if(!innobase_file_flush_method ||
> +                        !strstr(innobase_file_flush_method, "O_DIRECT")) {
> +                        innobase_file_flush_method = 
> +                                srv_file_flush_method_str = (char*)"O_DIRECT";
> +                        fprintf(stderr, "InnoDB: using O_DIRECT due to atomic writes.\n");
> +                }
> +#endif
> +#ifdef HAVE_POSIX_FALLOCATE
> +                /* Due to a bug in directFS, using atomics needs  
> +                 * posix_fallocate to extend the file
> +                 * pwrite()  past end of the file won't work
> +                 */
> +                srv_use_posix_fallocate = TRUE;
> +#endif
> +        }

it'd be nice if you could try os_file_set_atomic_writes() here to see if
that works. This function creates and opens quite a few files, you could
use one of them to mark it for atomic writes, and if that would fail,
you'd disable atomic writes, and wouldn't change
innobase_file_flush_method and innobase_use_doublewrite.

Btw, why not to use posix_fallocate whenever it's available?
Or, at least, with its own --innodb-use-fallocate option?

Regards,
Sergei