[lkml]   [2006]   [Dec]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Linux disk performance.
On Mon, Dec 18, 2006 at 06:24:39PM +0545, Manish Regmi wrote:
> On 12/18/06, Arjan van de Ven <> wrote:
> >if you want truely really smooth writes you'll have to work for it,
> >since "bumpy" writes tend to be better for performance so naturally the
> >kernel will favor those.
> >
> >to get smooth writes you'll need to do a threaded setup where you do an
> >msync/fdatasync/sync_file_range on a frequent-but-regular interval from
> >a thread. Be aware that this is quite likely to give you lower maximum
> >performance than the batching behavior though.
> >
> Thanks...
> But isn't O_DIRECT supposed to bypass buffering in Kernel?

It is.

> Doesn't it directly write to disk?

Yes, but it still uses an IO scheduler.

> I tried to put fdatasync() at regular intervals but there was no
> visible effect.

In your first message you mentioned you were using an ancient 2.6.10
kernel. That kernel uses the anticipatory IO scheduler. Update to the
latest stable kernel ( at time of writing) and it will default
to the CFQ scheduler which has a smoother writeout, plus you can give
your process a different IO scheduling class and level (see

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2006-12-18 14:21    [W:0.075 / U:7.400 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site