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Re: [PATCH 0/6 v3] kvmalloc

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On Tue, Jan 24, 2017 at 04:17:52PM +0100, Michal Hocko wrote:
> On Thu 12-01-17 16:37:11, Michal Hocko wrote:
> > Hi,
> > this has been previously posted as a single patch [1] but later on more
> > built on top. It turned out that there are users who would like to have
> > __GFP_REPEAT semantic. This is currently implemented for costly >64B
> > requests. Doing the same for smaller requests would require to redefine
> > __GFP_REPEAT semantic in the page allocator which is out of scope of
> > this series.
> > 
> > There are many open coded kmalloc with vmalloc fallback instances in
> > the tree.  Most of them are not careful enough or simply do not care
> > about the underlying semantic of the kmalloc/page allocator which means
> > that a) some vmalloc fallbacks are basically unreachable because the
> > kmalloc part will keep retrying until it succeeds b) the page allocator
> > can invoke a really disruptive steps like the OOM killer to move forward
> > which doesn't sound appropriate when we consider that the vmalloc
> > fallback is available.
> > 
> > As it can be seen implementing kvmalloc requires quite an intimate
> > knowledge if the page allocator and the memory reclaim internals which
> > strongly suggests that a helper should be implemented in the memory
> > subsystem proper.
> > 
> > Most callers I could find have been converted to use the helper instead.
> > This is patch 5. There are some more relying on __GFP_REPEAT in the
> > networking stack which I have converted as well but considering we do
> > not have a support for __GFP_REPEAT for requests smaller than 64kB I
> > have marked it RFC.
> 
> Are there any more comments? I would really appreciate to hear from
> networking folks before I resubmit the series.

while this patchset was baking the bpf side switched to use bpf_map_area_alloc()
which fixes the issue with missing __GFP_NORETRY that we had to fix quickly.
See commit d407bd25a204 ("bpf: don't trigger OOM killer under pressure with map alloc")
it covers all kmalloc/vmalloc pairs instead of just one place as in this set.
So please rebase and switch bpf_map_area_alloc() to use kvmalloc().
Thanks

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Re: [PATCH 0/6 v3] kvmalloc Michal Hocko <mhocko@kernel.org> - 2017-01-24 16:20 +0100
  Re: [PATCH 0/6 v3] kvmalloc Eric Dumazet <eric.dumazet@gmail.com> - 2017-01-24 17:10 +0100
    Re: [PATCH 0/6 v3] kvmalloc Michal Hocko <mhocko@kernel.org> - 2017-01-25 14:20 +0100
  Re: [PATCH 0/6 v3] kvmalloc Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2017-01-24 20:20 +0100
    Re: [PATCH 0/6 v3] kvmalloc Michal Hocko <mhocko@kernel.org> - 2017-01-25 14:20 +0100
      Re: [PATCH 0/6 v3] kvmalloc Michal Hocko <mhocko@kernel.org> - 2017-01-25 14:30 +0100

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