Messages in this thread | | | Date | Wed, 7 Dec 2016 15:57:50 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v7 |
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On Wed, Dec 07, 2016 at 08:52:27AM -0600, Christoph Lameter wrote: > On Wed, 7 Dec 2016, Mel Gorman wrote: > > > SLUB has been the default small kernel object allocator for quite some time > > but it is not universally used due to performance concerns and a reliance > > on high-order pages. The high-order concerns has two major components -- > > SLUB does not rely on high order pages. It falls back to lower order if > the higher orders are not available. Its a performance concern. >
Ok -- While SLUB does not rely on high-order pages for functional correctness, it perfoms better if high-order pages are available.
> This is also an issue for various other kernel subsystems that really > would like to have larger contiguous memory area. We are often seeing > performance constraints due to the high number of 4k segments when doing > large scale block I/O f.e. >
Which is related to the fundamentals of fragmentation control in general. At some point there will have to be a revisit to get back to the type of reliability that existed in 3.0-era without the massive overhead it incurred. As stated before, I agree it's important but outside the scope of this patch.
-- Mel Gorman SUSE Labs
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