Date: Sat, 22 Jul 2000 18:57:05 +0930 From: Greg Lehey <grog@lemis.com> To: Chuck Paterson <cp@bsdi.com> Cc: Matthew Dillon <dillon@apollo.backplane.com>, David Greenman <dg@root.com>, freebsd-smp@freebsd.org Subject: ipending (was: SMP progress (was: Stepping on Toes)) Message-ID: <20000722185705.A10221@wantadilla.lemis.com> In-Reply-To: <200007051652.KAA14768@berserker.bsdi.com>; from cp@bsdi.com on Wed, Jul 05, 2000 at 10:52:23AM -0600 References: <200007051652.KAA14768@berserker.bsdi.com>
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On Wednesday, 5 July 2000 at 10:52:23 -0600, Chuck Paterson wrote:
>>
>> Jake Burkholder is porting the BSD/OS mutexes. I don't expect there
>> to be much of a difference in regards to your heavy-weight interrupt
>> work. I'm going to take a look at Jake's patchset tonight. I think
>> the only operational item we need to research is the sti/cli stuff in
>> the BSDI mutexes... we should be able to remove them at some point
>> (my interrupt code is already using the ipending mechanism to deal
>> with the scheduler mutex being active on the current cpu).
>>
>> If Jake's removed that, then we'll want to put it back in at some point
>> since it saves a significant amount of overhead ('sti' and 'cli' are
>> expensive instructions).
>
> I believe ipending wants to go away totally. It really
> isn't meaningful in the thread environment and the locked operations
> needed to support it once multiple processor are running
> in the kernel are more expensive the sti, cli.
After working through the code, I agree. It's complicated to
maintain, and it's not needed. Removing it also has helped me find a
number of places where I need to change things.
In a similar way, I'm removing interrupt mask copies in memory. We
still mask interrupts which aren't in use, but no others. If anybody
has any reason not to want to do this, we should talk about it.
Greg
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