Messages in this thread | | | Date | Wed, 07 Apr 2004 16:34:51 -0700 | From | "Martin J. Bligh" <> | Subject | Re: -mmX 4G patches feedback [numbers: how much performance impact] |
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--On Thursday, April 08, 2004 01:18:06 +0200 Andrea Arcangeli <andrea@suse.de> wrote:
> On Wed, Apr 07, 2004 at 04:21:44PM -0700, Martin J. Bligh wrote: >> Speaking of which, pte_highmem is stinking expensive itself. There's >> probably a large class of workloads that'd work with out pte_highmem >> if we had 4/4 split (or shared pagetables. Grrr ;-)) > > hey, I can add a sysctl in 5 minutes to disable pte_highmem at runtime, > why do you think it's expensive, it should be not, it's all atomic kmaps > only doing invlpg. The few workloads trashing on the ptes manipulation > needs pte_highmem anyways. If I thought it was expensive for any common > load the sysctl would be already there.
I measured it - IIRC it was 5-10% on kernel compile ... and that was on a high ratio NUMA which it should have made *better* (as with highmem, the PTEs can be allocated node locally). I'll try to dig up the old profiles.
M.
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