On Thu 31-08-17 09:55:25, Vlastimil Babka wrote: > On 08/23/2017 08:47 AM, Vlastimil Babka wrote: > > On 07/24/2017 02:38 PM, Michal Hocko wrote: > >> On Thu 20-07-17 15:40:26, Vlastimil Babka wrote: > >>> In init_pages_in_zone() we currently use the generic set_page_owner() > >>> function > >>> to initialize page_owner info for early allocated pages. This means we > >>> needlessly do lookup_page_ext() twice for each page, and more importantly > >>> save_stack(), which has to unwind the stack and find the corresponding > >>> stack > >>> depot handle. Because the stack is always the same for the initialization, > >>> unwind it once in init_pages_in_zone() and reuse the handle. Also avoid > >>> the > >>> repeated lookup_page_ext(). > >> > >> Yes this looks like an improvement but I have to admit that I do not > >> really get why we even do save_stack at all here. Those pages might > >> got allocated from anywhere so we could very well provide a statically > >> allocated "fake" stack trace, no? > > > > We could, but it's much simpler to do it this way than try to extend > > stack depot/stack saving to support creating such fakes. Would it be > > worth the effort? > > Ah, I've noticed we already do this for the dummy (prevent recursion) > stack and failure stack. So here you go. It will also make the fake > stack more obvious after "[PATCH 2/2] mm, page_owner: Skip unnecessary > stack_trace entries" is merged, which would otherwise remove > init_page_owner() from the stack.
Yes this is what I've had in mind. > ----8<---- > >From 9804a5e62fc768e12b86fd4a3184e692c59ebfd1 Mon Sep 17 00:00:00 2001 > From: Vlastimil Babka <[email protected]> > Date: Thu, 31 Aug 2017 09:46:46 +0200 > Subject: [PATCH] mm, page_owner: make init_pages_in_zone() faster-fix2 > > Create statically allocated fake stack trace for early allocated pages, per > Michal Hocko. Yes this looks good to me. I am just wondering why we need 3 different fake stacks. I do not see any code that would special case them when dumping traces. Maybe this can be done on top? > Signed-off-by: Vlastimil Babka <[email protected]> Anyway Acked-by: Michal Hocko <[email protected]> > --- > mm/page_owner.c | 30 +++++++++++++++--------------- > 1 file changed, 15 insertions(+), 15 deletions(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 54d49fc8035e..262503f3ea66 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -30,6 +30,7 @@ DEFINE_STATIC_KEY_FALSE(page_owner_inited); > > static depot_stack_handle_t dummy_handle; > static depot_stack_handle_t failure_handle; > +static depot_stack_handle_t early_handle; > > static void init_early_allocated_pages(void); > > @@ -53,7 +54,7 @@ static bool need_page_owner(void) > return true; > } > > -static noinline void register_dummy_stack(void) > +static __always_inline depot_stack_handle_t create_dummy_stack(void) > { > unsigned long entries[4]; > struct stack_trace dummy; > @@ -64,21 +65,22 @@ static noinline void register_dummy_stack(void) > dummy.skip = 0; > > save_stack_trace(&dummy); > - dummy_handle = depot_save_stack(&dummy, GFP_KERNEL); > + return depot_save_stack(&dummy, GFP_KERNEL); > } > > -static noinline void register_failure_stack(void) > +static noinline void register_dummy_stack(void) > { > - unsigned long entries[4]; > - struct stack_trace failure; > + dummy_handle = create_dummy_stack(); > +} > > - failure.nr_entries = 0; > - failure.max_entries = ARRAY_SIZE(entries); > - failure.entries = &entries[0]; > - failure.skip = 0; > +static noinline void register_failure_stack(void) > +{ > + failure_handle = create_dummy_stack(); > +} > > - save_stack_trace(&failure); > - failure_handle = depot_save_stack(&failure, GFP_KERNEL); > +static noinline void register_early_stack(void) > +{ > + early_handle = create_dummy_stack(); > } > > static void init_page_owner(void) > @@ -88,6 +90,7 @@ static void init_page_owner(void) > > register_dummy_stack(); > register_failure_stack(); > + register_early_stack(); > static_branch_enable(&page_owner_inited); > init_early_allocated_pages(); > } > @@ -529,13 +532,10 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct > zone *zone) > unsigned long pfn = zone->zone_start_pfn, block_end_pfn; > unsigned long end_pfn = pfn + zone->spanned_pages; > unsigned long count = 0; > - depot_stack_handle_t init_handle; > > /* Scan block by block. First and last block may be incomplete */ > pfn = zone->zone_start_pfn; > > - init_handle = save_stack(0); > - > /* > * Walk the zone in pageblock_nr_pages steps. If a page block spans > * a zone boundary, it will be double counted between zones. This does > @@ -588,7 +588,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct > zone *zone) > continue; > > /* Found early allocated page */ > - __set_page_owner_handle(page_ext, init_handle, 0, 0); > + __set_page_owner_handle(page_ext, early_handle, 0, 0); > count++; > } > cond_resched(); > -- > 2.14.1 > -- Michal Hocko SUSE Labs
