Messages in this thread | | | Date | Wed, 19 Mar 2014 13:46:51 +0000 | From | Dietmar Eggemann <> | Subject | Re: [PATCH v2 2/7] sched: rework of sched_domain topology definition |
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On 19/03/14 12:41, Peter Zijlstra wrote: > > The keyboard deity gave us delete, please apply graciously when replying > to large emails.
Sorry about that, will do next time.
> > 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.
I see your point. So what we want to avoid is to enable archs to create different (per-cpu) set-ups inside a domain (as a specific set of cpu's from a viewpoint of a cpu) but misconfiguration of the whole domain is a different story. Got it!
> > 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. >
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