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Date: Wed, 21 Mar 2018 13:01:13 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
Subject: Re: [PATCH] slab: introduce the flag SLAB_MINIMIZE_WASTE
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To: Matthew Wilcox <willy@infradead.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, dm-devel@redhat.com, Mike Snitzer <msnitzer@redhat.com>

On Wed, 21 Mar 2018, Matthew Wilcox wrote:

> I don't know if that's a good idea.  That will contribute to fragmentation
> if the allocation is held onto for a short-to-medium length of time.
> If the allocation is for a very long period of time then those pages
> would have been unavailable anyway, but if the user of the tail pages
> holds them beyond the lifetime of the large allocation, then this is
> probably a bad tradeoff to make.
>
> I do see Mikulas' use case as interesting, I just don't know whether it's
> worth changing slab/slub to support it.  At first blush, other than the
> sheer size of the allocations, it's a good fit.

Well there are numerous page pool approaches already in the kernel. Maybe
there is a better fit with those?