Re: [PATCHv5] mm: optimization on page allocation when CMA enabled

[Zhaoyang Huang]

On Tue, Oct 10, 2023 at 9:31 AM Roman Gushchin <roman.gushchin@xxxxxxxxx> wrote:
>
> On Mon, Oct 09, 2023 at 05:14:15PM -0700, Andrew Morton wrote:
> > On Sun, 8 Oct 2023 15:54:40 +0800 Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote:
> >
> > > > Roman previously asked
> > > >
> > > > : Also I'm a bit concerned about potential performance implications.
> > > > : Would be great to provide some benchmarks or some data.  Probably it's
> > > > : ok because of we have pcp caches on top, but I'm not 100% sure.
> > > >
> > > > Are you able to perform such testing and tell us the result?
> > > I have applied this patch in a v5.4 based ANDROID system and got no
> > > regression problem. Actually, this commit is aimed to have
> > > alloc_pages(GFP_USER) use CMA instead of stealing U&R(could lead to
> > > GFP_KERNEL fail) only when zone's free pages and free cma are around
> > > WATERMARK_LOW/MIN which would NOT affect most scenarios.
> >
> > OK, thanks.
> >
> > Could the appropriate people please take a look at this?  It has been
> > in mm-unstable since May.
>
> I have 2 concerns:
> 1) it's still hard to understand the commit message and comments, I can
>    only reverse-engineer it based on the code changes;
> 2) performance concerns I expressed earlier are not addressed. Idk what's
>    a good benchmark for the page allocator, probably something i/o or
>    networking heavy.
>
ok, I will update the commit message

> On the positive side I believe that the patch is solving a real problem.