linux-kernel - Re: [patch 04/13] syslets: core code

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Message-ID: <Pine.LNX.4.64.0702241306070.17345@alien.or.mcafeemobile.com>
Date:	Sat, 24 Feb 2007 13:10:33 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 04/13] syslets: core code

On Sat, 24 Feb 2007, Ingo Molnar wrote:

> * Davide Libenzi <davidel@...ilserver.org> wrote:
> 
> > > +asmlinkage long
> > > +sys_threadlet_on(unsigned long restore_stack,
> > > +		 unsigned long restore_eip,
> > > +		 struct async_head_user __user *ahu)
> 
> > > +asmlinkage long sys_threadlet_off(void)
> 
> > If we have a new syscall that does the exec, we can save the two 
> > on/off calls.
> 
> the on/off calls are shaped in a way that makes them ultimately 
> vsyscall-able - the kernel only needs to know about the fact that we are 
> in a threadlet (so that the scheduler can do its special 
> push-head-to-another-context thing) - and this can be signalled via a 
> small user-space-side info structure as well, put into the TLS.

IMO it's not a matter of speed. We'll have those two new syscalls, that I 
don't see other practical use for. IMO the best thing would be to hide all 
inside the sys_threadlet_exec (or whatever name).




> > [...] Also, the complete_thread() thingy can be done automatically 
> > from inside the kernel upon function return, by hence making the 
> > threadlet function look like a normal thread function:
> 
> yeah - and that's how it works in my current codebase already, 
> threadlet_off() takes a 'completion event' pointer as well, and the ahu. 
> I'll release v4 so that you can have a look.

Ok. Will look into it...



- Davide


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