Re: [RFC][PATCH] delay accounting taskstats interface send tgid once

[Jay Lan <jlan@sgi.com>]

Shailabh,

Is this patch supposed to go on top of all other patches? Or is it
supposed to replace any? I had failure applying this patch on top
of all previously applied.

- jay


Shailabh Nagar wrote:
> Send per-tgid data only once during exit of a thread group instead of once with
> each member thread exit.
> 
> Currently, when a thread exits, besides its per-tid data, the per-tgid data of
> its thread group is also sent out, if its thread group is non-empty. The
> per-tgid data sent consists of the sum of per-tid stats for all *remaining*
> threads of the thread group.
> 
> This patch modifies this sending in two ways:
> 
> - the per-tgid data is sent only when the last thread of a thread group exits.
> This cuts down heavily on the overhead of sending/receiving per-tgid data,
> especially  when other exploiters of the taskstats interface aren't interested
> in per-tgid stats
> 
> - the semantics of the per-tgid data sent are changed. Instead of being the
> sum of per-tid data for remaining threads, the value now sent is the true total
> accumalated statistics for all threads that are/were part of the thread group.
> 
> The patch also addresses a minor issue where failure of one accounting
> subsystem to fill in the taskstats structure was causing the send of taskstats
> to not be sent at all.
> 
> The patch has been tested for stability and run cerberus for over 4 hours on
> an SMP.
> 
> Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>
> Signed-off-by: Balbir Singh <balbir@in.ibm.com>