Messages in this thread | | | Date | Mon, 9 Jan 2023 22:29:11 -0800 | Subject | Re: [PATCH] perf lock contention: Do not use BPF task local storage | From | Martin KaFai Lau <> |
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On 1/9/23 7:29 PM, Hou Tao wrote: > Hi Martin, > > On 1/10/2023 5:22 AM, Martin KaFai Lau wrote: >> On 1/9/23 12:56 PM, Namhyung Kim wrote: >>> Hello, >>> >>> On Mon, Nov 21, 2022 at 9:33 AM Martin KaFai Lau <martin.lau@linux.dev> wrote: >>>> >>>> On 11/18/22 11:01 AM, Namhyung Kim wrote: >>>>> We could fix the task local storage to use the safe BPF allocator, >>>>> but it takes time so let's change this until it happens actually. >>>> >>>> I also got another report on the kfree_rcu path. I am also looking into this >>>> direction on using the BPF allocator. >>> >>> Any progress on this? Are there any concerns about the change? >> >> Yep, I am working on it. It is not a direct replacement from kzalloc to >> bpf_mem_cache_alloc. eg. Some changes in the bpf mem allocator is needed to >> ensure the free list cannot be reused before the rcu grace period. There is a >> similar RFC patchset going into this direction that I am trying with. >> >> . > Do you mean "[RFC PATCH bpf-next 0/6] bpf: Handle reuse in bpf memory alloc" > [0], right ? Yes, that is the RFC patch I was referring :). I was planning to comment after looking at the patch in details. I have shared some of my quick thoughts in that thread for the local storage usages.
> The main concern [1] for the proposal is the possibility of OOM > will increase when RCU tasks trace grace period is slow, because the immediate > reuse is disabled and the reuse is only possible after one RCU tasks trace grace > period. Using a memory cgroup and setting a hard-limit on the cgroup may reduce > the influence of the OOM problem, but it is not good enough. So do you have > other ways to mitigate the potential OOM problem ? > > [0]: https://lore.kernel.org/bpf/20221230041151.1231169-1-houtao@huaweicloud.com/ > [1]: > https://lore.kernel.org/bpf/CAADnVQ+z-Y6Yv2i-icAUy=Uyh9yiN4S1AOrLd=K8mu32TXORkw@mail.gmail.com/
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