Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 19 Mar 2014 14:33:35 +0100 | Subject | Re: [PATCH v2 2/7] sched: rework of sched_domain topology definition |
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On 19 March 2014 13:41, Peter Zijlstra <peterz@infradead.org> wrote: > > The keyboard deity gave us delete, please apply graciously when replying > to large emails. > > On Wed, Mar 19, 2014 at 11:27:12AM +0000, Dietmar Eggemann wrote: >> On 18/03/14 17:56, Vincent Guittot wrote: >> > + if (sd->flags & SD_SHARE_CPUPOWER) { >> > + sd->imbalance_pct = 110; >> > + sd->smt_gain = 1178; /* ~15% */ >> > + sd->flags |= arch_sd_sibling_asym_packing(); >> > + >> > + } else if (sd->flags & SD_SHARE_PKG_RESOURCES) { >> > + sd->imbalance_pct = 117; >> > + sd->cache_nice_tries = 1; >> > + sd->busy_idx = 2; >> > + >> > +#ifdef CONFIG_NUMA >> > + } else if (sd->flags & SD_NUMA) { >> > + sd->cache_nice_tries = 2; >> > + sd->busy_idx = 3; >> > + sd->idle_idx = 2; >> > + >> > + sd->flags |= SD_SERIALIZE; >> > + if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) { >> > + sd->flags &= ~(SD_BALANCE_EXEC | >> > + SD_BALANCE_FORK | >> > + SD_WAKE_AFFINE); >> > + } >> > + >> > +#endif >> > + } else { >> > + sd->flags |= SD_PREFER_SIBLING; >> > + sd->cache_nice_tries = 1; >> > + sd->busy_idx = 2; >> > + sd->idle_idx = 1; >> > + } >> >> This 'if ... else statement' is still a weak point from the perspective >> of making the code robust: > > <snip> > >> Is there a way to check that MC and GMC have to have >> SD_SHARE_PKG_RESOURCES set so that this can't happen unnoticed? > > So from the core codes perspective those names mean less than nothing. > Its just a string to carry along for us meat-bags. The string isn't even > there when !SCHED_DEBUG. > > So from this codes POV you told it it had a domain without PKGSHARE, > that's fine. > > That said; yeah the thing isn't the prettiest piece of code. But it has > the big advantage of being the one place where we convert topology into > behaviour.
We might add a check of the child in sd_init to ensure that the child has at least some properties of the current level. I mean that if a level has got the SD_SHARE_PKG_RESOURCES flag, its child must also have it. The same for SD_SHARE_CPUPOWER and SD_ASYM_PACKING.
so we can add something like the below in sd_init
child_flags = SD_SHARE_PKG_RESOURCES | SD_SHARE_CPUPOWER | SD_ASYM_PACKING flags = sd->flags & child_flags if (sd->child) child_flags &= sd->child->flags child_flags &= flags if (flags != child_flags) pr_info("The topology description looks strange \n");
Vincent
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