[patch, libgfortran] PR33985 access="stream",form="unformatted" doesn't buffer

[Janne Blomqvist]

Thomas Koenig wrote:
> On Mon, 2007-12-03 at 11:45 +0100, Angelo Graziosi wrote:
>   
>> I do not think to my eyes... (ref.[1])
>>     
>
> Buffering is ok now:
>
>
>
> Offhand, I don't see what else we could do (except maybe increase
> our buffer size).
>
>   

I tested increasing the buffer size a year or so ago, and didn't see
much benefit. Of course, at that time we still had plenty of issues with
excessive flushing (wouldn't surprise me if we still do). However,
increasing buffer size might help on NFS, or does the kernel coalesce
I/O before sending it over the wire? In addition to that, exotic stuff
like Lustre on Cray XT wants buffers on the order of 10 MB, though I
think that's quite excessive for general purpose usage.

One thing that could help performance on some seeky workloads would be
to have multiple cache buckets, like a direct-mapped cache. To which
extent these would help outside contrived microbenchmarks I don't know.

-- 
Janne Blomqvist


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 252 bytes
Desc: OpenPGP digital signature
URL: <http://gcc.gnu.org/pipermail/fortran/attachments/20071203/e07dc3ea/attachment.sig>