linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Message-ID: <Pine.LNX.4.64.0702281259430.6806@alien.or.mcafeemobile.com>
Date:	Wed, 28 Feb 2007 13:09:47 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Ulrich Drepper <drepper@...hat.com>,
	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>,
	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 00/13] Syslets, "Threadlets", generic AIO support, v3

On Wed, 28 Feb 2007, Ingo Molnar wrote:

> 
> * Davide Libenzi <davidel@...ilserver.org> wrote:
> 
> > My point is, the syslet infrastructure is expensive for the kernel in 
> > terms of compat, [...]
> 
> it is not. Today i've implemented 64-bit syslets on x86_64 and 
> 32-bit-on-64-bit compat syslets. Both the 64-bit and the 32-bit syslet 
> (and threadlet) binaries work just fine on a 64-bit kernel, and they 
> share 99% of the infrastructure. There's only a single #ifdef 
> CONFIG_COMPAT in kernel/async.c:
> 
> #ifdef CONFIG_COMPAT
> 
> asmlinkage struct syslet_uatom __user *
> compat_sys_async_exec(struct syslet_uatom __user *uatom,
>                       struct async_head_user __user *ahu)
> {
>         return __sys_async_exec(uatom, ahu, &compat_sys_call_table,
>                                 compat_NR_syscalls);
> }
> 
> #endif

Did you hide all the complexity of the userspace atom decoding inside 
another function? :)
How much code would go away, in case we pick a simple/parallel 
sys_async_exec engine? Atoms decoding, special userspace variable access 
for loops, jumps/cond/... VM engine.



> Even mixed-mode syslets should work (although i havent specifically 
> tested them), where the head switches between 64-bit and 32-bit mode and 
> submits syslets from both 64-bit and from 32-bit mode, and at the same 
> time there might be both 64-bit and 32-bit syslets 'in flight'.
> 
> But i'm happy to change the syslet API in any sane way, and did so based 
> on feedback from Jens who is actually using them.

Wouldn't you agree on a simple/parallel execution engine like me and Linus 
are proposing (and threadlets, of course)?



- Davide


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