[LTP] [PATCH v4 0/4] Basic eBPF tests

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> On Mon, 2019-08-26 at 10:29 -0400, Jan Stancek wrote:
> > 
> > ----- Original Message -----
> > > I've ended up playing with the patchset and fixed a few loose ends
> > > on
> > > the map test and as I had the code at hand I decided to send v4
> > > instead
> > > of pointing out the mistakes in a review.
> > > 
> > > There were numerous small changes for the map test:
> > > 
> > > * Make sure the key buffer is sized exactly for the content
> > > 
> > > * Initialized the array/hash element value in test setup
> > > 
> > > * Made the code flow a bit more obvious, it was hard to tell which
> > >   part was run for n == 0 and which for n == 1
> > > 
> > > Also it looks that for me the test that loads the eBPF program ends
> > > up
> > > with EPERM randomly at about 10th iteration both as unpriviledged
> > > and
> > > priviledged user, which is really strange.
> > 
> > There's one EPERM I can reproduce reliably with bpf_map test, which
> > appears
> > to originate from "bpf_charge_memlock".
> > 
> > There's a deferred component to map freeing, and unchange appears to
> > be part of it:
> >   bpf_map_release
> >     bpf_map_put
> >       INIT_WORK(&map->work, bpf_map_free_deferred);
> >         (deferred) bpf_uncharge_memlock
> > 
> > When I lower max locked memory, it's easy to hit:
> > # ulimit  -l 128; ./bpf_map01 -i 100
> > ...
> > bpf_map01.c:52: CONF: bpf() requires CAP_SYS_ADMIN on this system:
> > EPERM
> > 
> > Can you try bumping max locked memory to some high value and check
> > if that helps your case?
> 
> # for i in 64 128 256 1024; do
>     echo $i;
>     ulimit -l $i;
>     ./bpf_prog01 -i 100 |& grep -P 'passed|CONF';
> done
> 
> 64
> CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
> passed   16
> 
> 128
> CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
> passed   16
> 
> 256
> CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
> passed   32
> 
> 1024
> CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
> passed   192
> 
> 
> Which produce almost the same results.
> Same approach with `bpf_map01` differs a lot. Sometimes all pass,
> sometimes none.

Seems to make difference for me on 5.2:

# cat bench.sh; sh bench.sh 
for i in 128 256 512 1024 4096 65536; do
        echo $i;
        ulimit -l $i;
        ./bpf_prog01 -i 100 |& grep -P 'passed|CONF';
        sleep 4;
done

128
bpf_prog01.c:114: CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
passed   32
256
bpf_prog01.c:114: CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
passed   64
512
bpf_prog01.c:114: CONF: bpf() requires CAP_SYS_ADMIN on this system: EPERM
passed   128
1024
passed   200
4096
passed   200
65536
passed   200