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Date: Sat, 29 Mar 2014 09:14:34 -0400 From: Tejun Heo <tj@...nel.org> To: Jianyu Zhan <nasa4836@...il.com> Cc: linux-mm@...ck.org, akpm@...ux-foundation.org, cl@...ux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] mm/percpu.c: don't bother to re-walk the pcpu_slot list if nobody free space since we last drop pcpu_lock On Fri, Mar 28, 2014 at 08:55:57PM +0800, Jianyu Zhan wrote: > Quoted tj: > >Hmmm... I'm not sure whether the added complexity is worthwhile. It's > >a fairly cold path. Can you show how helpful this optimization is? > > The patch is quite less intrusive in the normal path > and if we fall on the cold path, it means after satifying this allocation > the chunk may be moved to lower slot, and the follow-up allocation > of same or larger size(though rare) is likely to fail to cold path again. So > this patch could be based on to do some heuristic later. The above really doesn't show how helpful it is. This adds complexity to optimize what seemingly is a quite cold path, which often is a pretty bad idea as they tend to trade off readability and long term maintainability for almost non-existing actual gain. If you think this is a worthwhile optimization, please give justifications - use scenarios, performance numbers and so on. Thanks. -- tejun -- 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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