Re: [PATCH 3/5] mm/vmalloc.c: correct lazy_max_pages() return value

[Michal Hocko]

On Thu 22-09-16 09:13:50, zijun_hu wrote:
> On 09/22/2016 08:35 AM, David Rientjes wrote:
[...]
> > The intent is as it is implemented; with your change, lazy_max_pages() is 
> > potentially increased depending on the number of online cpus.  This is 
> > only a heuristic, changing it would need justification on why the new 
> > value is better.  It is opposite to what the comment says: "to be 
> > conservative and not introduce a big latency on huge systems, so go with
> > a less aggressive log scale."  NACK to the patch.
> > 
> my change potentially make lazy_max_pages() decreased not increased, i seems
> conform with the comment
> 
> if the number of online CPUs is not power of 2, both have no any difference
> otherwise, my change remain power of 2 value, and the original code rounds up
> to next power of 2 value, for instance
> 
> my change : (32, 64] -> 64
> 	     32 -> 32, 64 -> 64
> the original code: [32, 63) -> 64
>                    32 -> 64, 64 -> 128

You still completely failed to explain _why_ this is an improvement/fix
or why it matters. This all should be in the changelog.

-- 
Michal Hocko
SUSE Labs