linux-kernel - Re: [PATCH bpf 0/4] bpf_prog_pack and vmalloc-on-huge-page fixes

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Date:   Fri, 22 Apr 2022 07:42:32 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Song Liu <song@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     bpf@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        kernel-team@...com, akpm@...ux-foundation.org,
        rick.p.edgecombe@...el.com, hch@...radead.org,
        imbrenda@...ux.ibm.com
Subject: Re: [PATCH bpf 0/4] bpf_prog_pack and vmalloc-on-huge-page fixes

On Thu, Apr 21, 2022 at 10:18:09PM -0700, Song Liu wrote:
> NOTE: This set is based on Linus' master branch (d569e86915b7), not
> bpf/master.
> 
> There are various discussion about these changes, check out [1] [2].
> I guess we can use this thread to discuss which patches should go in 5.18.
> AFAICT, 1/4 need to with 5.18;

Since huge pages are effectively disabled on v5.18 I can't see why.

> 2/4 seems safe to go as well;

My impression on the discussion was that huge pages design was broken
and evidence for this came up after x86 finally enabled *a small*
portion use case of it. This revealed how broken huge pages were not
just for x86 but for other architectures. And so I can't see why we'd
enable for v5.18 huge pages for the large system hash.

> 3/4 and 4/4
> may still need more work/discussion.

Happy to review these but if huge pages are disabled I don't see the
point in a module_alloc_huge() yet.

  Luis

> 
> Thanks!
> 
> [1] https://lore.kernel.org/linux-mm/20220415164413.2727220-1-song@kernel.org/
> [2] https://lore.kernel.org/linux-mm/20220421072212.608884-1-song@kernel.org/
> 
> Song Liu (4):
>   bpf: invalidate unused part of bpf_prog_pack
>   page_alloc: use vmalloc_huge for large system hash
>   module: introduce module_alloc_huge
>   bpf: use module_alloc_huge for bpf_prog_pack
> 
>  arch/x86/kernel/module.c     | 21 +++++++++++++++++++++
>  arch/x86/net/bpf_jit_comp.c  | 22 ++++++++++++++++++++++
>  include/linux/bpf.h          |  2 ++
>  include/linux/moduleloader.h |  5 +++++
>  kernel/bpf/core.c            | 28 +++++++++++++++++++++-------
>  kernel/module.c              |  8 ++++++++
>  mm/page_alloc.c              |  2 +-
>  7 files changed, 80 insertions(+), 8 deletions(-)
> 
> --
> 2.30.2