lkml.org 
[lkml]   [2018]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch] mm, oom: fix unnecessary killing of additional processes
On Fri 22-06-18 11:49:14, David Rientjes wrote:
> On Fri, 22 Jun 2018, Michal Hocko wrote:
>
> > > > preempt_disable() is required because it calls kvm_kick_many_cpus() with
> > > > wait == true because KVM_REQ_APIC_PAGE_RELOAD sets KVM_REQUEST_WAIT and
> > > > thus the smp_call_function_many() is going to block until all cpus can run
> > > > ack_flush().
> > >
> > > I will make sure to talk to the maintainer of the respective code to
> > > do the nonblock case correctly.
> >
> > I've just double checked this particular code and the wait path and this
> > one is not a sleep. It is a busy wait for IPI to get handled. So this
> > one should be OK AFAICS. Anyway I will send an RFC and involve
> > respective maintainers to make sure I am not making any incorrect
> > assumptions.
>
> Do you believe that having the only potential source of memory freeing
> busy waiting for all other cpus on the system to run ack_flush() is
> particularly dangerous given the fact that they may be allocating
> themselves?

These are IPIs. How could they depend on a memory allocation? In other
words we do rely on the very same mechanism for TLB flushing so this is
any different.

Maybe I am missing something here though.

--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2018-06-25 11:05    [W:0.086 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site