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

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Date:   Wed, 7 Nov 2018 16:59:49 +0000
From:   Martin Lau <kafai@...com>
To:     Quentin Monnet <quentin.monnet@...ronome.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

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?

> 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>