On 06/03/14 09:04, Vincent Guittot wrote:
On 6 March 2014 07:17, Dietmar Eggemann dietmar.eggemann@arm.com wrote:
On 05/03/14 07:18, Vincent Guittot wrote:
This patchset was previously part of the larger tasks packing patchset [1]. I have splitted the latter in 3 different patchsets (at least) to make the thing easier. -configuration of sched_domain topology (this patchset) -update and consolidation of cpu_power -tasks packing algorithm
Based on Peter Z's proposal [2][3], this patchset modifies the way to configure the sched_domain level in order to let architectures to add specific level like the current BOOK level or the proposed power gating level for ARM architecture.
[1] https://lkml.org/lkml/2013/10/18/121 [2] https://lkml.org/lkml/2013/11/5/239 [3] https://lkml.org/lkml/2013/11/5/449
Vincent Guittot (6): sched: remove unused SCHED_INIT_NODE sched: rework of sched_domain topology definition sched: s390: create a dedicated topology table sched: powerpc: create a dedicated topology table sched: add a new SD_SHARE_POWERDOMAIN for sched_domain sched: ARM: create a dedicated scheduler topology table
arch/arm/kernel/topology.c | 26 ++++ arch/ia64/include/asm/topology.h | 24 ---- arch/metag/include/asm/topology.h | 27 ----- arch/powerpc/kernel/smp.c | 35 ++++-- arch/s390/include/asm/topology.h | 13 +- arch/s390/kernel/topology.c | 25 ++++ arch/tile/include/asm/topology.h | 33 ------ include/linux/sched.h | 30 +++++ include/linux/topology.h | 128 ++------------------ kernel/sched/core.c | 235 ++++++++++++++++++------------------- 10 files changed, 237 insertions(+), 339 deletions(-)
Hi Vincent,
I reviewed your patch-set carefully (including test runs on TC2), especially due to the fact that we want to build our sd_energy stuff on top of it.
Thanks
One thing I'm still not convinced of is the fact that specifying additional sd levels in the struct sched_domain_topology_level table has an advantage over a function pointer for sd topology flags similar to the one we're already using for the cpu mask in struct sched_domain_topology_level.
int (*sched_domain_flags_f)(int cpu);
We have to create additional level for some kind of topology as described in my trial https://lkml.org/lkml/2013/12/18/279 which is not possible with function pointer.
This is what I don't understand at the moment. In your example in the link above, (2 cluster of 4 cores with SMT), cpu 0-7 can powergate while cpu 8-15 can't). Why can't we have
static inline int cpu_coregroup_flags(int cpu) { int flags = SD_SHARE_PKG_RESOURCES;
if (cpu >= 8) flags |= SD_SHARE_POWERDOMAIN;
return flags; }
inside the arch specific topology file and use it in the MC level as the int (*sched_domain_flags_f)(int cpu) member of struct sched_domain_topology_level?
Have you got a situation in mind where it will be necessary to use the function pointer with cpu number as an argument ?
The one above. Fundamentally all situations where you want to set sd topology flags differently for different cpus in the same sd level. big.LITTLE is another example but it's the same as powergated/!powergated in this perspective.
In the current example of this patchset, the flags are statically set in the table but nothing prevents an architecture to update the flags value before being given to the scheduler
What will be the infrastructure if the arch wants to do so?
Thanks,
-- Dietmar
This function pointer would be simply another member of struct sched_domain_topology_level and would replace int sd_flags. AFAICS, you have to create additional cpu mask functions anyway for the additional sd levels, like cpu_corepower_mask() for the GMC level in the ARM case. There could be a set of standard sd topology flags function for the default sd layer and archs which want to pass in something special define those function locally since they will use them only in their arch specific struct sched_domain_topology_level table anyway. I know that you use the existing sd degenerate functionality for this and that the freeing of the redundant data structures (sched_domain, sched_group and sched_group_power) is there too but it still doesn't seem to me to be the right thing to do.
The problem that we now expose internal data structures (struct sd_data and struct sched_domain_topology_level) could be dealt with later.
-- Dietmar