From: Donald Hunter <donald.hunter@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <olsajiri@gmail.com>,
bpf@vger.kernel.org, linux-doc@vger.kernel.org,
dave@dtucker.co.uk, Alexei Starovoitov <ast@kernel.org>
Subject: Re: [PATCH bpf-next v6 1/1] bpf, docs: document BPF_MAP_TYPE_ARRAY
Date: Fri, 07 Oct 2022 17:07:53 +0100 [thread overview]
Message-ID: <m2fsfzborq.fsf@gmail.com> (raw)
In-Reply-To: <4b2cc38f-7ea8-56ad-30b3-af91553028ec@iogearbox.net> (Daniel Borkmann's message of "Fri, 7 Oct 2022 16:54:29 +0200")
Daniel Borkmann <daniel@iogearbox.net> writes:
> On 10/6/22 1:36 PM, Jiri Olsa wrote:
>> I recently hit 32k size limit for per-cpu map value.. it seems to be
>> size limit for generic per cpu allocation, but would be great to have
>> it confirmed by somebody who knows mm better ;-)
>
> Yes, for percpu the max is PCPU_MIN_UNIT_SIZE which is 32k, see mm/percpu.c +1756.
> In many cases it's implementation specific, so it probably does not make too much
> sense to state limits like 2^32, or at least it should say that its theoretical/uapi
> limit and actual limits may be implementation/config specific.
Yes, good point. I will just drop the 2^32 bit. Same issue was
raised by Stanislav Fomichev for BPF_MAP_TYPE_HASH here:
https://patchwork.kernel.org/project/netdevbpf/patch/20220713211612.84782-1-donald.hunter@gmail.com/#24936386
prev parent reply other threads:[~2022-10-07 16:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-05 10:46 [PATCH bpf-next v6 0/1] Document BPF_MAP_TYPE_ARRAY Donald Hunter
2022-10-05 10:46 ` [PATCH bpf-next v6 1/1] bpf, docs: document BPF_MAP_TYPE_ARRAY Donald Hunter
2022-10-06 11:36 ` Jiri Olsa
2022-10-07 14:54 ` Daniel Borkmann
2022-10-07 16:07 ` Donald Hunter [this message]
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