linux-kernel - Re: [PATCH] powerpc/8xx: reduce pressure on TLB due to context switches

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Message-ID: <1420599166.4961.47.camel@freescale.com>
Date:	Tue, 6 Jan 2015 20:52:46 -0600
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	"Joakim Tjernlund" <joakim.tjernlund@...nsmode.se>
Subject: Re: [PATCH] powerpc/8xx: reduce pressure on TLB due to context
 switches

On Mon, 2015-01-05 at 16:14 +0100, Christophe Leroy wrote:
> +		}
> +		__clear_bit(id, stale_map[cpu]);
> +
> +	}

Whitespace

> +
> +	/* Flush the TLB for all contexts */
> +	_tlbil_all();

Can you put a comment in here pointing out that for this to work on SMP,
it needs to be a global invalidation, or at least some indication on
this function that it's not SMP-safe?  I realize there's no SMP 8xx, and
this is only called in place of steal_context_up(), but in case others
think of reusing this elsewhere[1]...

-Scott

[1] It might be helpful on e500 derivatives in virtualized environments
where invalidate-by-PID is expensive, depending on how often stealing
happens there.

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