Messages in this thread |  | | Date | Wed, 2 Jan 2013 11:30:10 -0500 | From | Tejun Heo <> | Subject | Re: [PATCH 23/24] cfq-iosched: collect stats from dead cfqgs |
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Hey, Vivek.
On Wed, Jan 02, 2013 at 11:24:15AM -0500, Vivek Goyal wrote: > On Fri, Dec 28, 2012 at 12:35:45PM -0800, Tejun Heo wrote: > > To support hierarchical stats, it's necessary to remember stats from > > dead children. Add cfqg->dead_stats and make a dying cfqg transfer > > its stats to the parent's dead-stats. > > Hi Tejun, > > Why not directly transfer stats to cfqg->stats. IOW, what's the advantage > of maintaining dead_stats separately.
Backward compatibility? The existing stat cgroupfs files expect to see non-recursive stats.
> > + cfqg_stats_merge(&parent->dead_stats, &cfqg->stats); > > + cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats); > > + cfqg_stats_reset(&cfqg->stats); > > + cfqg_stats_reset(&cfqg->dead_stats); > > Anyway group will be marked offline and later freed. So resetting stats > might not be required.
Yeah, it isn't strictly necessary. I tried to transfer the residual IOs between offline and release first so the resetting. Kinda like them there tho.
> In fact if we have a realiable way of resetting status then online/offline > infrastructure might not be required? I think per cpu stats will be a > problem though and that's why we probably require logic to online/offline > the group?
Hmmm? What do you mean?
Thanks.
-- tejun
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