Messages in this thread |  | | Date | Wed, 2 Jan 2013 11:44:15 -0500 | From | Vivek Goyal <> | Subject | Re: [PATCH 23/24] cfq-iosched: collect stats from dead cfqgs |
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On Wed, Jan 02, 2013 at 11:30:10AM -0500, Tejun Heo wrote: > 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.
Oh yes. Missed that. So dead_stats makes sense.
[..] > > 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?
I mean if we had a reliable way of resetting stats after transferring then we would not need to keep a track of whether group is online/offline. We could add everything and adding zero will not change anything. In fact it will also take care of residual IO (IO which happened after transfer of stats).
Or I missed the real reason of why do we have group online/offline infrastructure.
Thanks Vivek
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