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Date: Thu, 07 Sep 2006 17:44:14 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: [Xenomai-core] Re: [RFC][PATCH] optimise wakeup order in
	xnsynch_flush
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Jan Kiszka wrote:
> Hi,
>=20
> this is so far a mind experiment combined with an untested patch:
>=20
> [Assuming priority lists, the following is irrelevant for O(1) sched-qu=
eues]
>=20
> Consider we have some bulk of threads with varying priorities waiting o=
n
> a xnsynch object. Typically, they are queued in priority order, the
> highest prio thread at the head. When we wake them up all at once via
> xnsynch_flush, we iterate from high to low prio threads.
>=20
> Waking up includes inserting those threads in the ready queue(s), again=

> the highest prio thread first. On wake up of the first waiting thread w=
e
> will only have to skip those threads in the ready queue that have highe=
r
> priorities. For the second thread we already have to skip the first one=

> as well on insert if it isn't of the same priority. One may continue
> this workflow...

Forget about this, there was a sign mistake: ready-queue walk already
takes place in the reverse order (from lower to higher prios), thus with
minimal iterations for the sketched scenario. Time to go home...

Jan


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