Re: [HACKERS] fsync method checking

Kurt Roeckx wrote:
> Here are my results on Linux 2.6.1 using cvs version 1.7.
>
> Those times with > 20 seconds, you really hear the disk go crazy.
>
> And I have the feeling something must be wrong.  Those results
> are reproducible.
>

Wow, your O_SYNC times are great.  Where can I buy some?  :-)

Anyway, we do need to find a way to test this because obviously there is
huge platform variability.

---------------------------------------------------------------------------


>
> Kurt
>
>
> Simple write timing:
>         write                    0.139558
>
> Compare fsync times on write() and non-write() descriptor:
> (If the times are similar, fsync() can sync data written
>  on a different descriptor.)
>         write, fsync, close      8.249364
>         write, close, fsync      8.356813
>
> Compare one o_sync write to two:
>         one 16k o_sync write    28.487650
>         two 8k o_sync writes     2.310304
>
> Compare file sync methods with one 8k write:
>         (o_dsync unavailable)
>         open o_sync, write       1.010688
>         write, fdatasync        25.109604
>         write, fsync,           26.051218
>
> Compare file sync methods with 2 8k writes:
> (The fastest should be used for wal_sync_method)
>         (o_dsync unavailable)
>         open o_sync, write       2.212223
>         write, fdatasync        27.439907
>         write, fsync,           27.772294
>
>
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