[blkfront] max_segments & max_segment_size

[blkfront] max_segments & max_segment_size

[Olivier Bonvalet]

Hi,

I have (very) poor write performance with Xen PV, used over RBD, and I
suppose it's because of very short values for max_segments and
max_segment_size.
(I have 250MB/s write speed in Dom0 vs 40MB/s write speed in DomU)

>From what I read, there is already a patch to fix that, called "multi
page ring support for block devices" : 
   http://lists.xen.org/archives/html/xen-devel/2012-03/msg00388.html

But it doesn't seem to have been accepted.

So, does it exist an other solution to fix that kind of problem ?

Thanks,
Olivier

Re: [blkfront] max_segments & max_segment_size

[Konrad Rzeszutek Wilk]

On Sat, Feb 09, 2013 at 06:44:22PM +0100, Olivier Bonvalet wrote:
> Hi,
> 
> I have (very) poor write performance with Xen PV, used over RBD, and I
> suppose it's because of very short values for max_segments and
> max_segment_size.
> (I have 250MB/s write speed in Dom0 vs 40MB/s write speed in DomU)
> 
> >From what I read, there is already a patch to fix that, called "multi
> page ring support for block devices" : 
>    http://lists.xen.org/archives/html/xen-devel/2012-03/msg00388.html
> 
> But it doesn't seem to have been accepted.
> 
> So, does it exist an other solution to fix that kind of problem ?

They are in development.
> 
> Thanks,
> Olivier
> 
> 
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