Re: [PATCH v8 1/4] vmalloc: Add __vmalloc_node_try_addr function

[Andrew Morton]

On Fri,  2 Nov 2018 12:25:17 -0700 Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> wrote:

> Create __vmalloc_node_try_addr function that tries to allocate at a specific
> address without triggering any lazy purging. In order to support this behavior
> a try_addr argument was plugged into several of the static helpers.

Please explain (in the changelog) why lazy purging is considered to be
a problem.  Preferably with some form of measurements, or at least a
hand-wavy guesstimate of the cost.

> This also changes logic in __get_vm_area_node to be faster in cases where
> allocations fail due to no space, which is a lot more common when trying
> specific addresses.