From: Song Liu <songliubraving@fb.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Song Liu <song@kernel.org>, bpf <bpf@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
Kernel Team <Kernel-team@fb.com>,
"Peter Zijlstra" <peterz@infradead.org>, X86 ML <x86@kernel.org>
Subject: Re: [PATCH v5 bpf-next 7/7] bpf, x86_64: use bpf_prog_pack allocator
Date: Fri, 21 Jan 2022 18:56:39 +0000 [thread overview]
Message-ID: <ACCB0C73-9968-4DB8-9B8D-97560B32D8DD@fb.com> (raw)
In-Reply-To: <CAADnVQLWj6cVE=OEqNfSBcAzFJDHPF8sPfqGfaCknV+Q=1HOmQ@mail.gmail.com>
> On Jan 21, 2022, at 10:29 AM, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Jan 21, 2022 at 9:53 AM Song Liu <songliubraving@fb.com> wrote:
>>>
>>> the header->size could be just below 2MB.
>>> I don't think kzalloc() can handle that.
>>
>> Technically, kzalloc can handle 2MB allocation via:
>> kzalloc() => kmalloc() => kmalloc_large() => kmalloc_order()
>>
>> But this would fail when the memory is fragmented. I guess we should use
>> kvmalloc() instead?
>
> Contiguous 2MB allocation?
Yeah, I tried that both kzalloc() and kvmalloc() could get 2MB memory.
I think kzalloc will fail when the memory is fragmented, but I haven't
confirmed it yet.
>
>>>
>>>> + if (!tmp_header) {
>>>> + bpf_jit_binary_free_pack(header);
>>>> + header = NULL;
>>>> + prog = orig_prog;
>>>> + goto out_addrs;
>>>> + }
>>>> + tmp_header->size = header->size;
>>>> + tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
>>>
>>> Why is 'tmp_image' needed at all?
>>> The above math can be done where necessary.
>>
>> We pass both image and tmp_image to do_jit(), as it needs both of them.
>> I think maintaining a tmp_image variable makes the logic cleaner. We can
>> remove it from x64_jit_data, I guess.
>
> I'd remove from x64_jit_data. The recompute is cheap.
Will do.
>
> Speaking of tmp_header name... would be great to come up
> with something more descriptive.
> Here both tmp_header/tmp_image and header/image are used at the same time.
> My initial confusion with the patch was due to the name 'tmp'.
> The "tmp" prefix implies that the tmp_image will be used first
> and then it will become an image.
> But it's not the case.
> Maybe call it 'rw_header' and add a comment that 'header/image'
> are not writeable directly ?
> Or call it 'poke_header' ?
> Other ideas?
I think rw_header/rw_image is good. poke_header is confusing, as we will
text_poke "header".
Thanks,
Song
next prev parent reply other threads:[~2022-01-21 18:56 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 19:12 [PATCH v5 bpf-next 0/7] bpf_prog_pack allocator Song Liu
2022-01-20 19:12 ` [PATCH v5 bpf-next 1/7] x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP Song Liu
2022-01-20 19:13 ` [PATCH v5 bpf-next 2/7] bpf: use bytes instead of pages for bpf_jit_[charge|uncharge]_modmem Song Liu
2022-01-20 19:13 ` [PATCH v5 bpf-next 3/7] bpf: use size instead of pages in bpf_binary_header Song Liu
2022-01-20 19:13 ` [PATCH v5 bpf-next 4/7] bpf: add a pointer of bpf_binary_header to bpf_prog Song Liu
2022-01-20 19:13 ` [PATCH v5 bpf-next 5/7] x86/alternative: introduce text_poke_copy Song Liu
2022-01-21 9:52 ` Peter Zijlstra
2022-01-20 19:13 ` [PATCH v5 bpf-next 6/7] bpf: introduce bpf_prog_pack allocator Song Liu
2022-01-20 19:13 ` [PATCH v5 bpf-next 7/7] bpf, x86_64: use " Song Liu
2022-01-21 4:59 ` Alexei Starovoitov
2022-01-21 17:53 ` Song Liu
2022-01-21 18:29 ` Alexei Starovoitov
2022-01-21 18:56 ` Song Liu [this message]
2022-01-21 1:06 ` [PATCH v5 bpf-next 0/7] " Song Liu
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