Hi Reinette,
On 2/21/2025 4:48 PM, Reinette Chatre wrote:
Hi Babu,
On 2/21/25 10:23 AM, Moger, Babu wrote:
Hi All,
On 2/21/2025 11:14 AM, Dave Martin wrote:
Hi,
On Thu, Feb 20, 2025 at 09:08:17AM -0800, Reinette Chatre wrote:
Hi Dave,
On 2/20/25 5:40 AM, Dave Martin wrote:
On Thu, Feb 20, 2025 at 11:35:56AM +0100, Peter Newman wrote:
Hi Reinette,
On Wed, Feb 19, 2025 at 6:55 PM Reinette Chatre
<reinette.chatre@xxxxxxxxx> wrote:
[...]
Could you please remind me how a user will set this flag?
Quoting my original suggestion[1]:
"info/L3_MON/mbm_assign_on_mkdir?
boolean (parsed with kstrtobool()), defaulting to true?"
After mount, any groups that got counters on creation would have to be
cleaned up, but at least that can be done with forward progress once
the flag is cleared.
I was able to live with that as long as there aren't users polling for
resctrl to be mounted and immediately creating groups. For us, a
single container manager service manages resctrl.
[...]
+1
That's basically my position -- the auto-assignment feels like a
_potential_ nuisance for ABMC-aware users, but it depends on what they
are trying to do. Migration of non-ABMC-aware users will be easier for
basic use cases if auto-assignment occurs by default (as in this
series).
Having an explicit way to turn this off seems perfectly reasonable
(and could be added later on, if not provided in this series).
What about the question re whether turning mbm_cntr_assign mode on
should trigger auto-assignment?
Currently turning this mode off and then on again has the effect of
removing all automatic assignments for extant groups. This feels
surprising and/or unintentional (?)
Connecting to what you start off by saying I also see auto-assignment
as the way to provide a smooth transition for "non-ABMC-aware" users.
I agree, and having this on by default also helps non-ABMC-aware users.
To me a user that turns this mode off and then on again can be
considered as a user that is "ABMC-aware" and turning it "off and then
on again" seems like an intuitive way to get to a "clean slate"
wrt counter assignments. This may also be a convenient way for
an "ABMC-aware" user space to unassign all counters and thus also
helpful if resctrl supports the flag that Peter proposed. The flag
seems to already keep something like this in its context with
a name of "mbm_assign_on_mkdir" that could be interpreted as
"only auto assign on mkdir"?
Yes, that's reasonable. It could be a good idea to document this
behaviour of switching the mbm_cntr_assign mode, if we think it is
useful and people are likely to rely on it.
Since mkdir is an implementation detail of the resctrl interface, I'd
be tempted to go for a more generic name, say,
"mbm_assign_new_mon_groups". But that's just bikeshedding.
The proposed behaviour seems fine.
Either way, if this is not included in this series, it could be added
later without breaking anything.
How about more generic "mbm_cntr_assign_auto" ?
I would like to be careful to not make it _too_ generic. Dave already pointed
out that users may be surprised that counters are not auto-assigned when switching
between the different modes so using the the name to help highlight when this
auto-assignment can be expected to happen seems very useful.
In that case "mbm_assign_on_mkdir" seems on point and precise.
Thanks
Babu
