Re: fallocate / posix_fallocate for new WAL file creation (etc...)

On Sun, Jun 30, 2013 at 11:52 PM, Greg Smith <greg@2ndquadrant.com> wrote:
> On 6/30/13 9:28 PM, Jon Nelson wrote:
>>
>> The performance of the latter (new) test sometimes seems to perform
>> worse and sometimes seems to perform better (usually worse) than
>> either of the other two. In all cases, posix_fallocate performs
>> better, but I don't have a sufficiently old kernel to test with.
>
>
> This updated test program looks reliable now.  The numbers are very tight
> when I'd expect them to be, and there's nowhere with the huge differences I
> saw in the earlier test program.
>
> Here's results from a few sets of popular older platforms:

If you found yourself with a spare moment, could you run these again
with the number of open/close cycles set high (say, 100) and the
number of rewrites set to 0 and also to 1? Most of the time spent is
actually spent overwriting the files so by reducing or eliminating
that aspect it might be easier to get a handle on the actual
performance difference.



--
Jon