Re: [PATCH 0/6 v3] kvmalloc

From: Michal Hocko
Date: Tue Jan 24 2017 - 10:18:09 EST

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.


> [1]

Michal Hocko