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Date: Mon, 3 Mar 2008 09:50:00 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: hpa@zytor.com, tglx@linutronix.de, andi@firstfloor.org, hch@infradead.org,
       linux-kernel@vger.kernel.org, Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: [patch 1/2] x86, fpu: split FPU state from task struct - v2
Message-ID: <20080303085000.GB15943@elte.hu>
References: <20080301005141.997705000@linux-os.sc.intel.com>
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* Suresh Siddha <suresh.b.siddha@intel.com> wrote:

> Split the FPU save area from the task struct. This allows easy 
> migration of FPU context, and it's generally cleaner. It also allows 
> the following two optimizations:
> 
> 1) only allocate when the application actually uses FPU, so in the 
> first lazy FPU trap. This could save memory for non-fpu using apps. 
> Next patch does this lazy allocation.
> 
> 2) allocate the right size for the actual cpu rather than 512 bytes 
> always. Patches enabling xsave/xrstor support (coming shortly) will 
> take advantage of this.

thanks, i've applied your two patches to x86.git#testing.

the #ifdefs are still a bit ugly:

> +#ifndef arch_task_cache_init
> +#define arch_task_cache_init()
> +#endif

use a __weak alias instead. (that way if an architecture defines the 
function, that function takes over automatically at link time, without 
any #ifdef complications)

> +#ifndef arch_dup_task_struct
> +static inline int arch_dup_task_struct(struct task_struct *dst,
> +				       struct task_struct *src)
> +{
> +	*dst = *src;
> +	return 0;
> +}
> +#endif

ditto.

	Ingo