Re: [PATCH bpf-next v9 2/6] mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Tue, Mar 11, 2025 at 3:04 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 21 Feb 2025 18:44:23 -0800 Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>
> > Tracing BPF programs execute from tracepoints and kprobes where
> > running context is unknown, but they need to request additional
> > memory. The prior workarounds were using pre-allocated memory and
> > BPF specific freelists to satisfy such allocation requests.
>
> The "prior workarounds" sound entirely appropriate.  Because the
> performance and maintainability of Linux's page allocator is about
> 1,000,040 times more important than relieving BPF of having to carry a
> "workaround".

Please explain where performance and maintainability is affected?

As far as motivation, if I recall correctly, you were present in
the room when Vlastimil presented the next steps for SLUB at
LSFMM back in May of last year.
A link to memory refresher is in the commit log:
https://lwn.net/Articles/974138/

Back then he talked about a bunch of reasons including better
maintainability of the kernel overall, but what stood out to me
as the main reason to use SLUB for bpf, objpool, mempool,
and networking needs is prevention of memory waste.
All these wrappers of slub pin memory that should be shared.
bpf, objpool, mempools should be good citizens of the kernel
instead of stealing the memory. That's the core job of the
kernel. To share resources. Memory is one such resource.