netdev - Re: [PATCH 00/24] Split page pools from struct page

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Date:   Mon, 5 Dec 2022 17:44:46 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>, brouer@...hat.com,
        netdev@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 00/24] Split page pools from struct page

Hi Jesper,

On Mon, Dec 05, 2022 at 04:34:10PM +0100, Jesper Dangaard Brouer wrote:
> 
> On 30/11/2022 23.07, Matthew Wilcox (Oracle) wrote:
> > The MM subsystem is trying to reduce struct page to a single pointer.
> > The first step towards that is splitting struct page by its individual
> > users, as has already been done with folio and slab.  This attempt chooses
> > 'netmem' as a name, but I am not even slightly committed to that name,
> > and will happily use another.
> 
> I've not been able to come-up with a better name, so I'm okay with
> 'netmem'.  Others are of-cause free to bikesheet this ;-)

Same here. But if anyone has a better name please shout.

> 
> > There are some relatively significant reductions in kernel text
> > size from these changes.  I'm not qualified to judge how they
> > might affect performance, but every call to put_page() includes
> > a call to compound_head(), which is now rather more complex
> > than it once was (at least in a distro config which enables
> > CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP).
> > 
> 
> I have a micro-benchmark [1][2], that I want to run on this patchset.
> Reducing the asm code 'text' size is less likely to improve a
> microbenchmark. The 100Gbit mlx5 driver uses page_pool, so perhaps I can
> run a packet benchmark that can show the (expected) performance improvement.
> 
> [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/bench_page_pool_simple.c
> [2] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/bench_page_pool_cross_cpu.c
> 

If you could give it a spin it would be great.  I did apply the patchset
and was running fine on my Arm box. I was about to run these tests, but then
I remembered that this only works for x86.  I don't have any cards supported
by page pool around.

> > I've only converted one user of the page_pool APIs to use the new netmem
> > APIs, all the others continue to use the page based ones.
> > 
> 
> I guess we/netdev-devels need to update the NIC drivers that uses page_pool.
> 
 
[...]

Regards
/Ilias