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From: Davide Libenzi <davidel@xmailserver.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linux Kernel List <linux-kernel@vger.kernel.org>,
	rmk+lkml@arm.linux.org.uk
Subject: Re: scheduler: IRQs disabled over context switches
Date: Mon, 24 May 2004 10:16:57 -0700 (PDT)	[thread overview]
Message-ID: <Pine.LNX.4.58.0405241012300.4174@bigblue.dev.mdolabs.com> (raw)
In-Reply-To: <20040524090538.GA26183@elte.hu>

On Mon, 24 May 2004, Ingo Molnar wrote:

> 
> * Davide Libenzi <davidel@xmailserver.org> wrote:
> 
> > We used to do it in 2.4. What changed to make it fragile? The
> > threading (TLS) thing?
> 
> it _should_ work, but in the past we only had trouble from such changes
> (at least in the O(1) tree of scheduling - 2.4 scheduler is OK.). We
> could try the patch below. It certainly boots on SMP x86. But it causes
> a 3.5% slowdown in lat_ctx so i'd not do it unless there are some really
> good reasons.

IMO it is fine, as long as it works with IRQ disabled. There are archs 
where IRQ latencies matters more than lat_ctx times (that BTW are bogus). 
And we already have the infrastructure in place to let the arch to choose 
the way better fits it. Russel reported that a guy trying it (IRQ enabled 
ctx switch) with MIPS was having some problem with it though.


BTW, the unlock_irq should go in prepare not finish.


- Davide


  parent reply	other threads:[~2004-05-24 17:17 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-23 16:43 Russell King
2004-05-23 18:59 ` Davide Libenzi
2004-05-23 19:38   ` Russell King
2004-05-23 23:04     ` Davide Libenzi
2004-05-23 23:33       ` Russell King
2004-05-24  0:27         ` Davide Libenzi
2004-05-24  8:37 ` Ingo Molnar
2004-05-24  6:41   ` Davide Libenzi
2004-05-24  9:05     ` Ingo Molnar
2004-05-24  7:10       ` Nick Piggin
2004-05-24  9:15         ` Ingo Molnar
2004-05-24 17:16       ` Davide Libenzi [this message]
2004-05-24 17:46         ` Davide Libenzi

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