Messages in this thread | | | Date | Wed, 19 Mar 2014 15:22:39 +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 13:33, Vincent Guittot wrote: [...]
>>> 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");
I tried it with my faulty set-up on TC2 and I get the info message for the GMC level for all CPU's in sd_init.
I had to pass an 'struct sched_domain *child' pointer into sd_init() from build_sched_domain() because inside sd_init() sd->child is always NULL.
So one of the requirements of this approach is that a child level like GMC (which could potentially replace its parent level or otherwise is destroyed itself) has to specify all flags of its parent level (MC)?
What about SD_NUMA in child_flags? SD_ASYM_PACKING is also a little bit different than SD_SHARE_PKG_RESOURCES or SD_SHARE_CPUPOWER because it's not used in the if ... else statement.
But I'm afraid this only works for this specific case of the MC/GMC layer and is not scalable. If sd->child is a level for which you don't want to potentially destroy itself or its parent, then you would get false alarms. IMHO, sd_init() has no information for which pair of adjacent levels it should apply this check and for which not. Do I miss something here?
-- Dietmar
> > Vincent >
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