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
