From: Hou Tao <houtao@huaweicloud.com>
To: YiFei Zhu <zhuyifei@google.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Stanislav Fomichev <sdf@google.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Andrii Nakryiko <andrii@kernel.org>
Subject: Re: [PATCH bpf 1/2] bpf/memalloc: Non-atomically allocate freelist during prefill
Date: Thu, 27 Jul 2023 09:21:44 +0800 [thread overview]
Message-ID: <8a8ab9b4-e2f1-9f53-f9ab-a3affadf332b@huaweicloud.com> (raw)
In-Reply-To: <CAA-VZPmretQpaGan_w=VMpvL_gKsAb_fT-x8Q4Eci8dE4EPvHQ@mail.gmail.com>
Hi,
On 7/27/2023 2:44 AM, YiFei Zhu wrote:
> On Wed, Jul 26, 2023 at 4:38 AM Hou Tao <houtao@huaweicloud.com> wrote:
>> Hi,
>>
>> On 7/21/2023 10:31 AM, YiFei Zhu wrote:
>>> On Thu, Jul 20, 2023 at 6:45 PM Hou Tao <houtao@huaweicloud.com> wrote:
>>>> On 7/21/2023 4:44 AM, YiFei Zhu wrote:
>>>>> Sometimes during prefill all precpu chunks are full and atomic
>>>>> __alloc_percpu_gfp would not allocate new chunks. This will cause
>>>>> -ENOMEM immediately upon next unit_alloc.
>>>>>
>>>>> Prefill phase does not actually run in atomic context, so we can
>>>>> use this fact to allocate non-atomically with GFP_KERNEL instead
>>>>> of GFP_NOWAIT. This avoids the immediate -ENOMEM. Unfortunately
>>>>> unit_alloc runs in atomic context, even from map item allocation in
>>>>> syscalls, due to rcu_read_lock, so we can't do non-atomic
>>>>> workarounds in unit_alloc.
>>>>>
>>>>> Fixes: 4ab67149f3c6 ("bpf: Add percpu allocation support to bpf_mem_alloc.")
>>>>> Signed-off-by: YiFei Zhu <zhuyifei@google.com>
>>>> Make sense to me, so
>>>>
>>>> Acked-by: Hou Tao <houtao1@huawei.com>
>>>>
>>>> But I don't know whether or not it is suitable for bpf tree.
>>> I don't mind either way :) If changing to bpf-next requires a resend I
>>> can do that too.
>> Please resend and rebase the patch again bpf-next tree.
>>
> Will do. Should I drop the Fixes tag then?
Before the introduction of bpf memory allocator, the allocation flag for
per-cpu memory allocation in hash map is GFP_NOWAIT. BPF memory
allocator doesn't change that, so I think we could drop the Fixes tag.
>
> YiFei Zhu
>
> .
next prev parent reply other threads:[~2023-07-27 1:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 20:44 [PATCH bpf 0/2] bpf/memalloc: Allow non-atomic alloc_bulk YiFei Zhu
2023-07-20 20:44 ` [PATCH bpf 1/2] bpf/memalloc: Non-atomically allocate freelist during prefill YiFei Zhu
2023-07-21 1:44 ` Hou Tao
2023-07-21 2:31 ` YiFei Zhu
2023-07-26 11:38 ` Hou Tao
2023-07-26 18:44 ` YiFei Zhu
2023-07-27 1:21 ` Hou Tao [this message]
2023-07-20 20:44 ` [PATCH bpf 2/2] bpf/memalloc: Schedule highprio wq for non-atomic alloc when atomic fails YiFei Zhu
2023-07-21 2:24 ` Hou Tao
2023-07-21 3:02 ` YiFei Zhu
2023-07-26 11:37 ` Hou Tao
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