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Date: Mon, 3 Jan 2011 08:58:15 -0500 From: Ted Ts'o <tytso@....edu> To: Pekka Enberg <penberg@...nel.org> Cc: Minchan Kim <minchan.kim@...il.com>, Christoph Lameter <cl@...ux-foundation.org>, Pekka Enberg <penberg@...helsinki.fi>, Matt Mackall <mpm@...enic.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, David Rientjes <rientjes@...gle.com>, npiggin@...nel.dk Subject: Re: Should we be using unlikely() around tests of GFP_ZERO? On Mon, Jan 03, 2011 at 09:40:57AM +0200, Pekka Enberg wrote: > I guess the rationale here is that if you're going to take the hit of > memset() you can take the hit of unlikely() as well. We're optimizing > for hot call-sites that allocate a small amount of memory and > initialize everything themselves. That said, I don't think the > unlikely() annotation matters much either way and am for removing it > unless people object to that. I suspect for many slab caches, all of the slab allocations for a given slab cache type will have the GFP_ZERO flag passed. So maybe it would be more efficient to zap the entire page when it is pressed into service for a particular slab cache, so we can avoid needing to use memset on a per-object basis? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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