cvs commit: src/sys/kern sched_ule.c

Robert Watson rwatson at
Sat Jan 20 16:11:47 UTC 2007

On Sat, 20 Jan 2007, Jeff Roberson wrote:

> jeff        2007-01-20 09:03:43 UTC
>  FreeBSD src repository
>  Modified files:
>    sys/kern             sched_ule.c
>  Log:
>   - In tdq_transfer() always set NEEDRESCHED when necessary regardless of
>     the ipi settings.  If NEEDRESCHED is set and an ipi is later delivered
>     it will clear it rather than cause extra context switches.  However, if
>     we miss setting it we can have terrible latency.
>   - In sched_bind() correctly implement bind.  Also be slightly more
>     tolerant of code which calls bind multiple times.  However, we don't
>     change binding if another call is made with a different cpu.  This
>     does not presently work with hwpmc which I believe should be changed.

sched_bind() appears not to be documented in scheduler(9), and the semantics 
you describe (bind requiring an unbind before a thread can be bound again) 
sound like something it would be useful to document, especially as schedulers 
differ on what is allowed?

Robert N M Watson
Computer Laboratory
University of Cambridge

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