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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 19 Apr 2022 19:18:50 -0700
Message-ID: <CAHk-=wiF1KnM1_paB3jCONR9Mh1D_RCsnXKBau1K7XLG-mwwTQ@mail.gmail.com>
Subject: Re: [PATCH v4 bpf 0/4] vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     Mike Rapoport <rppt@kernel.org>, Song Liu <songliubraving@fb.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        "mcgrof@kernel.org" <mcgrof@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
        "hch@infradead.org" <hch@infradead.org>,
        "ast@kernel.org" <ast@kernel.org>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "song@kernel.org" <song@kernel.org>,
        Kernel Team <Kernel-team@fb.com>,
        "pmladek@suse.com" <pmladek@suse.com>,
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On Tue, Apr 19, 2022 at 7:03 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> Here is the quote from Song's cover letter for bpf_prog_pack series:

I care about performance as much as the next person, but I care about
correctness too.

That large-page code was a disaster, and was buggy and broken.

And even with those four patches, it's still broken.

End result: there's no way that thigh gets re-enabled without the
correctness being in place.

At a minimum, to re-enable it, it needs (a) that zeroing and (b)
actual numbers on real loads. (not some artificial benchmark).

Because without (a) there's no way in hell I'll enable it.

And without (b), "performance" isn't actually an argument.

                  Linus