Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

[Joel Fernandes]

On Mon, Mar 11, 2019 at 12:32:33PM -0400, Joel Fernandes wrote:
> On Sun, Mar 10, 2019 at 01:34:03PM -0700, Sultan Alsawaf wrote:
> [...]
> >  
> >  	/* Perform scheduler related setup. Assign this task to a CPU. */
> >  	retval = sched_fork(clone_flags, p);
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 3eb01dedf..fd0d697c6 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -67,6 +67,7 @@
> >  #include <linux/lockdep.h>
> >  #include <linux/nmi.h>
> >  #include <linux/psi.h>
> > +#include <linux/simple_lmk.h>
> >  
> >  #include <asm/sections.h>
> >  #include <asm/tlbflush.h>
> > @@ -967,6 +968,11 @@ static inline void __free_one_page(struct page *page,
> >  		}
> >  	}
> >  
> > +#ifdef CONFIG_ANDROID_SIMPLE_LMK
> > +	if (simple_lmk_page_in(page, order, migratetype))
> > +		return;
> > +#endif
> > +
> >  	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> >  out:
> >  	zone->free_area[order].nr_free++;
> > @@ -4427,6 +4433,13 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >  	if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL))
> >  		goto nopage;
> >  
> > +#ifdef CONFIG_ANDROID_SIMPLE_LMK
> > +	page = simple_lmk_oom_alloc(order, ac->migratetype);
> > +	if (page)
> > +		prep_new_page(page, order, gfp_mask, alloc_flags);
> > +	goto got_pg;
> > +#endif
> > +
> 
> Hacking generic MM code with Android-specific callback is probably a major
> issue with your patch.
>
> Also I CC'd -mm maintainers and lists since your patch
> touches page_alloc.c. Always run get_maintainer.pl before sending a patch. I
> added them this time.

I see you CC'd linux-mm on your initial patch, so I apologize. Ignore this
part of my reply. Thanks.



> Have you looked at the recent PSI work that Suren and Johannes have been
> doing [1]?  As I understand, userspace lmkd may be migrated to use that at some
> point.  Suren can provide more details. I am sure AOSP contributions to make
> LMKd better by using the PSI backend would be appreciated. Please consider
> collaborating on that and help out, thanks. Check the cover-letter of that
> patch [1] where LMKd is mentioned.