Messages in this thread | | | Subject | Re: Suspicious error for CMA stress test | From | Vlastimil Babka <> | Date | Mon, 14 Mar 2016 08:06:16 +0100 |
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On 03/14/2016 07:49 AM, Joonsoo Kim wrote: > On Fri, Mar 11, 2016 at 06:07:40PM +0100, Vlastimil Babka wrote: >> On 03/11/2016 04:00 PM, Joonsoo Kim wrote: >> >> How about something like this? Just and idea, probably buggy (off-by-one etc.). >> Should keep away cost from <pageblock_order iterations at the expense of the >> relatively fewer >pageblock_order iterations. > > Hmm... I tested this and found that it's code size is a little bit > larger than mine. I'm not sure why this happens exactly but I guess it would be > related to compiler optimization. In this case, I'm in favor of my > implementation because it looks like well abstraction. It adds one > unlikely branch to the merge loop but compiler would optimize it to > check it once.
I would be surprised if compiler optimized that to check it once, as order increases with each loop iteration. But maybe it's smart enough to do something like I did by hand? Guess I'll check the disassembly.
> > Thanks. > >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index ff1e3cbc8956..b8005a07b2a1 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -685,21 +685,13 @@ static inline void __free_one_page(struct page *page, >> unsigned long combined_idx; >> unsigned long uninitialized_var(buddy_idx); >> struct page *buddy; >> - unsigned int max_order = MAX_ORDER; >> + unsigned int max_order = pageblock_order + 1; >> >> VM_BUG_ON(!zone_is_initialized(zone)); >> VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); >> >> VM_BUG_ON(migratetype == -1); >> - if (is_migrate_isolate(migratetype)) { >> - /* >> - * We restrict max order of merging to prevent merge >> - * between freepages on isolate pageblock and normal >> - * pageblock. Without this, pageblock isolation >> - * could cause incorrect freepage accounting. >> - */ >> - max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1); >> - } else { >> + if (likely(!is_migrate_isolate(migratetype))) { >> __mod_zone_freepage_state(zone, 1 << order, migratetype); >> } >> >> @@ -708,11 +700,12 @@ static inline void __free_one_page(struct page *page, >> VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page); >> VM_BUG_ON_PAGE(bad_range(zone, page), page); >> >> +continue_merging: >> while (order < max_order - 1) { >> buddy_idx = __find_buddy_index(page_idx, order); >> buddy = page + (buddy_idx - page_idx); >> if (!page_is_buddy(page, buddy, order)) >> - break; >> + goto done_merging; >> /* >> * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page, >> * merge with it and move up one order. >> @@ -729,6 +722,26 @@ static inline void __free_one_page(struct page *page, >> page_idx = combined_idx; >> order++; >> } >> + if (max_order < MAX_ORDER) { >> + if (IS_ENABLED(CONFIG_CMA) && >> + unlikely(has_isolate_pageblock(zone))) { >> + >> + int buddy_mt; >> + >> + buddy_idx = __find_buddy_index(page_idx, order); >> + buddy = page + (buddy_idx - page_idx); >> + buddy_mt = get_pageblock_migratetype(buddy); >> + >> + if (migratetype != buddy_mt && >> + (is_migrate_isolate(migratetype) || >> + is_migrate_isolate(buddy_mt))) >> + goto done_merging; >> + } >> + max_order++; >> + goto continue_merging; >> + } >> + >> +done_merging: >> set_page_order(page, order); >> >> /* >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> >
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