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SubjectRe: [PATCH] sched: Introduce TASK_NOLOAD and TASK_IDLE
On Sat, 9 May 2015 11:49:01 +0300 (EEST) Julian Anastasov <ja@ssi.bg> wrote:

>
> Hello,
>
> On Fri, 8 May 2015, Peter Zijlstra wrote:
>
> > Subject: sched: Introduce TASK_NOLOAD and TASK_IDLE
> > From: Peter Zijlstra <peterz@infradead.org>
> > Date: Fri May 8 14:23:45 CEST 2015
> >
> > Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for
> > 'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having
> > all idle kthreads contribute to the loadavg is somewhat silly.
> >
> > Now mostly this works OK, because kthreads have all their signals
> > masked. However there's a few sites where this is causing problems and
> > TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue.
> >
> > This patch adds TASK_NOLOAD which, when combined with
> > TASK_UNINTERRUPTIBLE avoids the loadavg accounting.
> >
> > As most of imagined usage sites are loops where a thread wants to
> > idle, waiting for work, a helper TASK_IDLE is introduced.
>
> After checking our code in net/netfilter/ipvs/ip_vs_sync.c,
> sync_thread_master(), we may also need some wrappers:
>
> - schedule_timeout_idle (instead of schedule_timeout call):
> __set_current_state(TASK_IDLE);
> return schedule_timeout(timeout);
>
> - we here are really idle, so "N" looks ok

yes, I would want
wait_event_idle_timeout() and wait_event_idle()

but I'll be happy to take whatever I can get :-)

Thanks,
NeilBrown


>
> - pair of __wait_event_idle(wq, condition) and
> wait_event_idle(wq, condition) macros
>
> - we here are write-blocked for socket, not sure
> if this blocked vs idle difference is useful to
> represent, in new bit for this blocked state "B"=2048,
> with 2 TASK_NOLOAD variants: N(idle) and B(blocked,
> 2|1024|2048, eg. for read-blocked or write-blocked).
> It will need additional argument 'state'/'blocked' for
> *wait_event_idle().
>
> Regards
>
> --
> Julian Anastasov <ja@ssi.bg>

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