Re: [PATCH 1/3] mm/vmalloc: fix possible exhaustion of vmalloc space caused by vm_map_ram allocator

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 17 Mar 2015 17:22:46 +0900 Roman Peniaev <r.peniaev@gmail.com> wrote:

> >> My second patch fixes this problem.
> >> I occupy the block on allocation and avoid jumping to the search loop.
> >
> > I'm not sure that this fixes above case.
> > 'vm_map_ram (3) * 85' means 85 times vm_map_ram() calls.
> >
> > First vm_map_ram(3) caller could get benefit from your second patch.
> > But, second caller and the other callers in each iteration could not
> > get benefit and should iterate whole list to find suitable free block,
> > because this free block is put to the tail of the list. Am I missing
> > something?
> 
> You are missing the fact that we occupy blocks in 2^n.
> So in your example 4 page slots will be occupied (order is 2), not 3.

Could you please

- update the changelogs so they answer the questions which Joonsoo
  Kim and Gioh Kim asked

- write a little in-kernel benchmark to test the scenario which
  Joonsoo described and include the before and after timing results in
  the changelogs

- resend the patchset

Thanks.

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