Re: [PATCH] mm/page_alloc: Wait for oom_lock before retrying.

[Michal Hocko <mhocko@suse.com>]

On Thu 15-12-16 10:11:42, Sergey Senozhatsky wrote:
> On (12/13/16 18:06), Michal Hocko wrote:
> [..]
> > What if we lower the loglevel as much as possible to only see KERN_ERR
> > should be sufficient to see few oom killer messages while suppressing
> > most of the other noise. Unfortunatelly, even messages with level >
> > loglevel get stored into the ringbuffer (as I've just learned) so
> > console_unlock() has to crawl through them just to drop them (Meh) but
> > at least it doesn't have to go to the serial console drivers and spend
> > even more time there. An alternative would be to tweak printk to not
> > even store those messaes. Something like the below
> > 
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index f7a55e9ff2f7..197f2b9fb703 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -1865,6 +1865,15 @@ asmlinkage int vprintk_emit(int facility, int level,
> >  				lflags |= LOG_CONT;
> >  			}
> >  
> > +			if (suppress_message_printing(kern_level)) {
> 
> aren't we supposed to check level here:
> 				suppress_message_printing(level)?
> 
> kern_level is '0' away from actual level:
> 
> 	kern_level = printk_get_level(text)
> 	switch (kern_level)
> 	case '0' ... '7':
> 		level = kern_level - '0';

Yes you are right. The patch would be broken for KERN_CONT so I think it
doesn't make much sense to pursue it for testing.

Thanks!
-- 
Michal Hocko
SUSE Labs

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