On Fri, Jul 01, 2022 at 06:29:20PM +0900, Hyeonggon Yoo wrote:
> On Fri, Jul 01, 2022 at 10:23:30AM +0800, Feng Tang wrote:
[snip]
> >
> > > And then it has overhead of 'waste' field for every non-kmalloc objects
> > > because track is saved per object. Also the field is not used at free.
> > > (Maybe that would be okay as it's only for debugging, just noting.)
> >
> > Yes, the field itself is a 'waste' for non-kmalloc objects :) I do
> > have another patch to add an option for this
> >
> > +config SLUB_DEBUG_KMALLOC_WASTE
> > + bool "Enable kmalloc memory waste debug"
> > + depends on SLUB_DEBUG && DEBUG_FS
> > ...
> >
> > And didn't post it due to the same debugging thought as you. And I can
> > add it back if it's really necessary.
>
> Let's see how others think :)
> I'm okay with current patch.
Okay.
> > > > mm/slub.c | 45 ++++++++++++++++++++++++++++++---------------
> > > > 1 file changed, 30 insertions(+), 15 deletions(-)
[snip]
> > > >
> > > > l->min_pid = track->pid;
> > > > l->max_pid = track->pid;
> > > > l->handle = handle;
> > > > + l->waste = track->waste;
> > >
> > > I think this may be fooled when there are different wastes values
> > > from same caller (i.e. when a kmalloc_track_caller() is used.)
> >
> > Yes, with the patch, we found quite some cases that the same caller
> > requests different sizes.
> >
> > > because the array is sorted by caller address, but not sorted by waste.
> >
> > In the patch we have in add_location():
> >
> > + if ((track->addr == caddr) && (handle == chandle) &&
> > + (track->waste == l->waste)) {
> >
> > Do you mean the following is missed?
> >
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -5176,6 +5176,8 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
> > end = pos;
> > else if (track->addr == caddr && handle < chandle)
> > end = pos;
> > + else if (track->addr == caddr && handle == chandle && track->waste < l->waste)
> > + end = pos;
> > else
> > start = pos;
> >
>
> Yes. Exactly. :)
Great, will add it in the next version. Thanks for cathing the errors!
- Feng
> Thanks,
> Hyeonggon
