Re: [PATCH 2/3] mm: separate memory allocation and actual work in alloc_vmap_area()

[Roman Gushchin <guro@fb.com>]

On Fri, Mar 01, 2019 at 03:43:19PM +0100, Vlastimil Babka wrote:
> On 2/25/19 9:30 PM, Roman Gushchin wrote:
> > alloc_vmap_area() is allocating memory for the vmap_area, and
> > performing the actual lookup of the vm area and vmap_area
> > initialization.
> > 
> > This prevents us from using a pre-allocated memory for the map_area
> > structure, which can be used in some cases to minimize the number
> > of required memory allocations.
> 
> Hmm, but that doesn't happen here or in the later patch, right? The only
> caller of init_vmap_area() is alloc_vmap_area(). What am I missing?

So initially the patch was a part of a bigger patchset, which
tried to minimize the number of separate allocations during vmalloc(),
e.g. by inlining vm_struct->pages into vm_struct for small areas.

I temporarily dropped the rest of the patchset for some rework,
but decided to leave this patch, because it looks like a nice refactoring
in any case, and also it has been already reviewed and acked by Matthew
and Johannes.

Thank you for looking into it!