linux-kernel - Re: [PATCH 4 of 4] Introduce aio system call submission and completion system calls

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Date:	31 Jan 2007 09:58:38 +0100
From:	Andi Kleen <ak@...e.de>
To:	Zach Brown <zach.brown@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-aio@...ck.org,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 4 of 4] Introduce aio system call submission and completion system calls

Zach Brown <zach.brown@...cle.com> writes:

> This finally does something useful with the notion of being able to schedule
> stacks as fibrils under a task_struct.  Again, i386-specific and in need of
> proper layering with archs.
> 
> sys_asys_submit() is added to let userspace submit asynchronous system calls.
> It specifies the system call number and arguments.  A fibril is constructed for
> each call.  Each starts with a stack which executes the given system call
> handler and then returns to a function which records the return code of the
> system call handler.  sys_asys_await_completion() then lets userspace collect
> these results.

Do you have any numbers how this compares cycle wise to just doing
clone+syscall+exit in user space? 

If the difference is not too big might it be easier to fix
clone+syscall to be more efficient than teach all the rest
of the kernel about fibrils? 

-Andi
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