| Message ID | 1425052454-25797-11-git-send-email-vincent.guittot@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 2 March 2015 at 12:52, Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote: > * Vincent Guittot <vincent.guittot@linaro.org> [2015-02-27 16:54:13]: > >> Add the SD_PREFER_SIBLING flag for SMT level in order to ensure that >> the scheduler will put at least 1 task per core. >> >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> >> Reviewed-by: Preeti U. Murthy <preeti@linux.vnet.ibm.com> >> --- >> kernel/sched/core.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 29f7037..753f0a2 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -6240,6 +6240,7 @@ sd_init(struct sched_domain_topology_level *tl, int cpu) >> */ >> >> if (sd->flags & SD_SHARE_CPUCAPACITY) { >> + sd->flags |= SD_PREFER_SIBLING; >> sd->imbalance_pct = 110; >> sd->smt_gain = 1178; /* ~15% */ >> > > Prefer siblings logic dates back to https://lkml.org/lkml/2009/8/27/210 > and only used in update_sd_lb_stats() where we have > > if (child && child->flags & SD_PREFER_SIBLING) > prefer_sibling = 1; > > However what confuses me is why should we even look at a child domain's > flag to balance tasks across the current sched domain? Why cant we just > set and use a sd flag at current level than to look at child domain > flag? Peter, have you got some insight about the reason ? egarding SMT, I see one advantage : the prefer sibling flag only need to be set if SMT is enable and a smt sched_domain is present but it implies some action at the parent level. If the flag was directly set at parent level, the behavior linked to SD_PREFER_SIBLING flag will be applied whatever the presence or not of the SMT domain. Regards, Vincent > >> -- >> 1.9.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ > > -- > Thanks and Regards > Srikar Dronamraju > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 29f7037..753f0a2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6240,6 +6240,7 @@ sd_init(struct sched_domain_topology_level *tl, int cpu) */ if (sd->flags & SD_SHARE_CPUCAPACITY) { + sd->flags |= SD_PREFER_SIBLING; sd->imbalance_pct = 110; sd->smt_gain = 1178; /* ~15% */