netdev - Re: [PATCH bpf 2/2] bpf: use vmalloc with VM_ALLOW_HUGE_VMAP for bpf_prog

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Message-ID: <87C3A212-AC47-4AC2-9A85-FD11F61715C0@fb.com>
Date:   Mon, 11 Apr 2022 22:18:17 +0000
From:   Song Liu <songliubraving@...com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Song Liu <song@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        Kernel Team <Kernel-team@...com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>,
        "imbrenda@...ux.ibm.com" <imbrenda@...ux.ibm.com>
Subject: Re: [PATCH bpf 2/2] bpf: use vmalloc with VM_ALLOW_HUGE_VMAP for
 bpf_prog_pack



> On Apr 10, 2022, at 11:56 PM, Christoph Hellwig <hch@...radead.org> wrote:
> 
> On Sun, Apr 10, 2022 at 01:34:50AM +0000, Song Liu wrote:
>> OTOH, it is probably beneficial for the modules to use something 
>> similar to bpf_prog_pack, i.e., put text from multiple modules to a 
>> single huge page. Of course, this requires non-trivial work in both 
>> mm code and module code.
>> 
>> Given that 1) modules cannot use huge pages yet, and 2) module may
>> use differently (with sharing), I think adding module_alloc_large()
>> doesn't add much value at the moment. So we can just keep this logic
>> in BPF for now. 
>> 
>> Does this make sense?
> 
> I'm not intending to say modules should use the new helper.  But I'd much
> prefer to keep all the MODULES_VADDR related bits self-contained in the
> modules code and not splatter it over random other subsystems.

Got it. Will add that in v2. 

Thanks,
Song