linux-kernel - Re: RFC: Kernel lock elision for TSX

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Message-ID: <20130323180010.GK20853@two.firstfloor.org>
Date:	Sat, 23 Mar 2013 19:00:10 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: RFC: Kernel lock elision for TSX

Hi Linux,

Thanks.  Other code/design review would be still appreciated, even
under the current constraints.

> The other comment I have is that since it does touch non-x86 header
> files etc (although not a lot), you really need to talk to the POWER8
> people about naming of the thing. Calling it <linux/rtm.h> and having
> "generic" helpers called _xtest() used by the generic spinlock code
> sounds a bit suspect.

I can make up another name for _xtest()/_xabort() and linux/rtm.h,
(any suggestions?)

The basic concepts implemented there should be pretty universal.
If others have a equivalent of "is this a transaction" and "abort
this tranction" they can just plug it in. Otherwise they will nop it,
as it's only hints anyways.

The only things used outside x86 code is _xtest()/_xabort(), can
remove the rest from linux/*. Without transactions this is all nops.
The primary interface for the lock code is the much higher level
elide()/elide_lock_adapt() interface anyways.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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