[LTP] [PATCH 1/3] lib: add functions to adjust oom score

[Li Wang]

Hi Petr,

On Thu, Dec 16, 2021 at 3:50 PM Petr Vorel <pvorel@suse.cz> wrote:

> Hi Li,
>
> > This introduces function to LTP for adjusting the oom_score_adj of
> > target process, which may be helpful in OOM tests to prevent kernel
> > killing the main or lib process during test running.
> very good idea.
>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
>
> > The exported global tst_enable_oom_protection function can be used
> > at anywhere you want to protect, but please remember that if you
> > do enable protection on a process($PID) that all the children will
> > inherit its score and be ignored by OOM Killer as well. So that's
> > why tst_cancel_oom_protection is recommended to combination in use.
>
> BTW deliberately not documenting it as it should not be commonly
>

Yes, actually it's not a commendatory API to users, and I think
we do really avoid using it unless we have no better choice.
(at least for OOM tests I can tell this)
The main reason we use it is current kernel OOM is not very
perfect, we just use it to help get the completed log for LTP.



> used in tests? Also although oom_score_adj inheritance should be known to
> person who will want to add it somewhere, I'd move it from commit message
> to
> source code (into header docs or or C API doc).
>

Sounds reasonable, will add this in V2.


>
> > +static void set_oom_score_adj(pid_t pid, int value)
> > +{
> > +     int val;
> > +     char score_path[64];
> > +
> > +     if (access("/proc/self/oom_score_adj", F_OK) == -1) {
> > +             tst_res(TINFO, "Warning: oom_score_adj is not exist");
> nit: IMHO "does not exist" or just "not exist"
>

Agree.

-- 
Regards,
Li Wang
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