linux-kernel - Re: sched_yield proposals/rationale

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Message-ID: <461E33BA.2030104@yahoo.com.au>
Date:	Thu, 12 Apr 2007 23:27:22 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Buytaert_Steven@....com
CC:	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: Re: sched_yield proposals/rationale

Buytaert_Steven@....com wrote:
>>-----Original Message-----
>>From: Andi Kleen
>>[ ... about use of sched_yield ...]
>>On the other hand when they fix their code to not rely on sched_yield
>>but use [...]
> 
> 
> Agreed, but $ find . -name "*.[ch]" | xargs grep -E "yield[ ]*\(" | wc over
> the 2.6.16 kernel yields 105 hits, note including comments...

Most of these (in core code, anyway) seem to use yield when they really don't
care about running for a while.

> An interesting spot is e.g. fs/buffer.c free_more_memory()

This one should be pretty rare (actually I think it is dead code in practice,
due to the way the page allocator works).

Avoiding sched_yield is a really good idea outside realtime scheduling. Since
we have gone this far with the current semantics, I think it would be sad to
back down now.

It would be nice if you could pressure those other components to adapt :)

-- 
SUSE Labs, Novell Inc.
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