On Thu, 30 Jul 2015, Marcelo Tosatti wrote:
On Thu, Jul 30, 2015 at 10:47:23AM -0700, Vikas Shivappa wrote:
Marcello,
On Wed, 29 Jul 2015, Marcelo Tosatti wrote:
How about this:
desiredclos (closid p1 p2 p3 p4)
1 1 0 0 0
2 0 0 0 1
3 0 1 1 0
#1 Currently in the rdt cgroup , the root cgroup always has all the
bits set and cant be changed (because the cgroup hierarchy would by
default make this to have all bits as all the children need to have
a subset of the root's bitmask). So if the user creates a cgroup and
not put any task in it , the tasks in the root cgroup could be still
using that part of the cache. Thats the reason i say we can have
really 'exclusive' masks.
Or in other words - there is always a desired clos (0) which has all
parts set which acts like a default pool.
Also the parts can overlap. Please apply this for all the below
comments which will change the way they work.
p means part.
I am assuming p = (a contiguous cache capacity bit mask)
closid 1 is a exclusive cgroup.
closid 2 is a "cache hog" class.
closid 3 is "default closid".
Desiredclos is what user has specified.
Transition 1: desiredclos --> effectiveclos
Clean all bits of unused closid's
(that must be updated whenever a
closid1 cgroup goes from empty->nonempty
and vice-versa).
effectiveclos (closid p1 p2 p3 p4)
1 0 0 0 0
2 0 0 0 1
3 0 1 1 0
Transition 2: effectiveclos --> expandedclos
expandedclos (closid p1 p2 p3 p4)
1 0 0 0 0
2 0 0 0 1
3 1 1 1 0
Then you have different inplacecos for each
CPU (see pseudo-code below):
On the following events.
- task migration to new pCPU:
- task creation:
id = smp_processor_id();
for (part = desiredclos.p1; ...; part++)
/* if my cosid is set and any other
cosid is clear, for the part,
synchronize desiredclos --> inplacecos */
if (part[mycosid] == 1 &&
part[any_othercosid] == 0)
wrmsr(part, desiredclos);
Currently the root cgroup would have all the bits set which will act
like a default cgroup where all the otherwise unused parts (assuming
they are a set of contiguous cache capacity bits) will be used.
Right, but we don't want to place tasks in there in case one cgroup
wants exclusive cache access.
So whenever you want an exclusive cgroup you'd do:
create cgroup-exclusive; reserve desired part of the cache
for it.
create cgroup-default; reserved all cache minus that of cgroup-exclusive
for it.
place tasks that belong to cgroup-exclusive into it.
place all other tasks (including init) into cgroup-default.
Is that right?
Yes you could do that.
You can create cgroups to have masks which are exclusive in todays
implementation, just that you could also created more cgroups to overlap the
masks again.. iow we dont have an exclusive flag for the cgroup mask.
Is that a common use case in
the server environment that you need to prevent other cgroups from using a
certain mask ? (since the root user should control these allocations .. he
should know?)
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