Subject: Re: [v3, 2/2] powerpc: Copy only required pieces of the mm_context_t to the paca

From: Michael Ellerman <[email-masked]>
Date: Mon, 11 Jan 2016 20:14:01 +1100 (AEDT)

On Thu, 2015-10-12 at 22:34:42 UTC, Michael Neuling wrote:
> Currently we copy the whole mm_context_t to the paca but only access a
> few bits of it.  This is wasteful of space paca and also takes quite
> some time in the hot path of context switching.
> 
> This patch pulls in only the required bits from the mm_context_t to
> the paca and on context switch, copies only those.
> 
> Benchmarking this (On top of Anton's recent MSR context switching
> changes [1]) using processes and yield shows an improvement of almost
> 3% on POWER8:
> 
>   http://ozlabs.org/~anton/junkcode/context_switch2.c
>   ./context_switch2 --test=yield --process 0 0
> 
> 1. https://lists.ozlabs.org/pipermail/linuxppc-dev/2015-October/135700.html
> 
> Signed-off-by: Michael Neuling <[email-masked]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/2fc251a8dda56b71ec491bee4c

cheers