Messages in this thread |  | | Date | Tue, 7 Jan 2020 13:28:09 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched, fair: Allow a small degree of load imbalance between SD_NUMA domains v2 |
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On Tue, Jan 07, 2020 at 12:22:55PM +0100, Peter Zijlstra wrote: > On Tue, Jan 07, 2020 at 09:56:55AM +0000, Mel Gorman wrote:
> > + unsigned int imbalance_adj; > > + > > + /* > > + * Calculate an acceptable degree of imbalance based > > + * on imbalance_adj. However, do not allow a greater > > + * imbalance than the child domains weight to avoid > > + * a case where the allowed imbalance spans multiple > > + * LLCs. > > + */ > > That comment is a wee misleading, @child is not an LLC per se. This > could be the NUMA distance 2 domain, in which case @child is the NUMA > distance 1 group. > > That said, even then it probably makes sense to ensure you don't idle a > whole smaller distance group.
Hmm, one more thing. On AMD EPYC, which the multiple LLCs, you'll have the single NODE domain in between, and that is not marked with SD_NUMA (iirc).
So specifically the case you want to handle is not in fact handled. The first SD_NUMA (distance-1) will have all NODE children, which on EPYC are not LLCs.
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