netdev - Re: [PATCH bpf-next] tools: bpftool: adjust rlimit RLIMIT

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Message-ID: <642a6b13-8f11-5cc2-80bc-4e7580824ddb@netronome.com>
Date:   Wed, 7 Nov 2018 17:03:14 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Martin Lau <kafai@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "oss-drivers@...ronome.com" <oss-drivers@...ronome.com>
Subject: Re: [PATCH bpf-next] tools: bpftool: adjust rlimit RLIMIT_MEMLOCK
 when loading programs, maps

2018-11-07 16:59 UTC+0000 ~ Martin Lau <kafai@...com>
> On Wed, Nov 07, 2018 at 12:29:30PM +0000, Quentin Monnet wrote:
>> The limit for memory locked in the kernel by a process is usually set to
>> 64 bytes by default. This can be an issue when creating large BPF maps
> hmm... 64 _k_bytes?

Ouch. That's true. Thanks! I can respin to fix the commit log if needed.

>> and/or loading many programs. A workaround is to raise this limit for
>> the current process before trying to create a new BPF map. Changing the
>> hard limit requires the CAP_SYS_RESOURCE and can usually only be done by
>> root user (for non-root users, a call to setrlimit fails (and sets
>> errno) and the program simply goes on with its rlimit unchanged).
>>
>> There is no API to get the current amount of memory locked for a user,
>> therefore we cannot raise the limit only when required. One solution,
>> used by bcc, is to try to create the map, and on getting a EPERM error,
>> raising the limit to infinity before giving another try. Another
>> approach, used in iproute2, is to raise the limit in all cases, before
>> trying to create the map.
>>
>> Here we do the same as in iproute2: the rlimit is raised to infinity
>> before trying to load programs or to create maps with bpftool.
>>
>> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
>> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Patch LGTM.
> 
> Acked-by: Martin KaFai Lau <kafai@...com>
> 

Thanks for this as well.
Quentin