Re: [Xen-devel] [PATCH v3 1/2] Interface for grant copy operation in libs.

[Paulina Szubarczyk <paulinaszubarczyk@xxxxxxxxx>]

On Wed, 22 Jun 2016 12:24:16 +0100
Wei Liu <wei.liu2@xxxxxxxxxx> wrote:

> On Wed, Jun 22, 2016 at 11:53:00AM +0200, Paulina Szubarczyk wrote:
> [...]
> > > I know Wei asked for this but you've replaced what should be a single
> > > pointer assignment with a memory allocation and two loops over all the
> > > segments.
> > > 
> > > This is a hot path and the two structures (the libxengnttab one and the
> > > Linux kernel one) are both part of their respective ABIs and won't
> > > change so Wei's concern that they might change in the future is unfounded.
> > > 
> > > This change makes xengnttab_grant_copy() useless for our (XenServer's)
> > > use case.
> > > 
> > > David
> > 
> > As Wei and Ian are maintainers of toolstack if they agree on the previous
> > cast that was here I will revert the changes.
> > 
> 
> Do you have the most up to date numbers? How do they compare to the
> numbers in previous version? If there is degradation, how big is that in
> terms of percentage?
> 
> Wei.
> 
In the file [1] in the sheets with *-domU there are the results for the new
implementation with comparisons to grant map implementation which I run
yesterday/today. I also rebase to the newest staging version before the tests
and there is some improvement for both grant map and grant copy implementation
comparing to previous results, that is way I would not compare the results from
the previous test and I am going to run the test for the implementation with
casting the structures again today. 

But single test that I made take around 90 minutes, since there is 5 min warm
up and 1 min x 14 size of blocks for iodepth in range [1, 4, 8, 64, 256]. And I
usually did them at least three times..

[1]https://docs.google.com/spreadsheets/d/1E6AMiB8ceJpExL6jWpH9u2yy6DZxzhmDUyFf-eUuJ0c/edit?usp=sharing

Paulina


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