Re: [PATCH v4 02/16] selftests/resctrl: Calculate resctrl FS derived mem bw over sleep(1) only

[Reinette Chatre]

Hi Ilpo,

On 5/30/24 4:11 AM, Ilpo Järvinen wrote:
> On Tue, 28 May 2024, Reinette Chatre wrote:
> > On 5/28/24 3:19 AM, Ilpo Järvinen wrote:
> > > On Fri, 24 May 2024, Ilpo Järvinen wrote:
> > > > On Fri, 24 May 2024, Reinette Chatre wrote:
> > > > > On 5/24/24 12:57 AM, Ilpo Järvinen wrote:
> > > > > > On Thu, 23 May 2024, Reinette Chatre wrote:

..

> > > > > It is not necessary to open and close the file every time a value needs
> > > > > to be read from it.
> > >
> > > I'm bit unsure where to go with this. While I could change the code to
> > > match what you described, I realized with the two files approach there's
> > > no need to do even review/lseek() call during the measurement. It might
> > > not be very significant compared with the open that was there initially
> > > but it's still extra.
> >
> > We are discussing the resctrl selftests that will accompany the resctrl
> > filesystem in the kernel. When in doubt on how to interact with resctrl users
> > use the selftests as reference. Needing to open and close a resctrl file
> > every time a value needs to be read from it is not the correct guidance.
>
> That's actually a different goal from the earlier, but I've no problem
> adjusting to it.
>
> Initially, this open/close() refactoring was made because of another goal
> which was to avoid doing extra syscalls during the test.

It is not clear what you hint at here. Reading twice from an open file
should not be a huge adjustment so it is not clear to me how this results
in a big change to this work. As I understand this does match with original goal
of reducing syscalls since the file need not be opened and closed twice.

Reinette