On 05/03/2016 07:22 AM, js1304@xxxxxxxxx wrote: > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > We don't need to split freepages with holding the zone lock. It will cause > more contention on zone lock so not desirable. Fair enough, I just worry about the same thing as Hugh pointed out recently [1] in that it increases the amount of tricky stuff in compaction.c doing similar but not quite the same stuff as page/alloc.c, and which will be forgotten to be updated once somebody updates prep_new_page with e.g. a new debugging check. Can you perhaps think of a more robust solution here? Thanks [1] http://marc.info/?i=alpine.LSU.2.11.1604270029350.7066%40eggly.anvils%3E > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > --- > include/linux/mm.h | 1 - > mm/compaction.c | 42 ++++++++++++++++++++++++++++++------------ > mm/page_alloc.c | 27 --------------------------- > 3 files changed, 30 insertions(+), 40 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 7b52750..9608f33 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -523,7 +523,6 @@ void __put_page(struct page *page); > void put_pages_list(struct list_head *pages); > > void split_page(struct page *page, unsigned int order); > -int split_free_page(struct page *page); > > /* > * Compound pages have a destructor function. Provide a > diff --git a/mm/compaction.c b/mm/compaction.c > index c9a95c1..ecf0252 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -65,13 +65,31 @@ static unsigned long release_freepages(struct list_head *freelist) > > static void map_pages(struct list_head *list) > { > - struct page *page; > + unsigned int i, order, nr_pages; > + struct page *page, *next; > + LIST_HEAD(tmp_list); > + > + list_for_each_entry_safe(page, next, list, lru) { > + list_del(&page->lru); > + > + order = page_private(page); > + nr_pages = 1 << order; > + set_page_private(page, 0); > + set_page_refcounted(page); > + > + arch_alloc_page(page, order); > + kernel_map_pages(page, nr_pages, 1); > + kasan_alloc_pages(page, order); > + if (order) > + split_page(page, order); > > - list_for_each_entry(page, list, lru) { > - arch_alloc_page(page, 0); > - kernel_map_pages(page, 1, 1); > - kasan_alloc_pages(page, 0); > + for (i = 0; i < nr_pages; i++) { > + list_add(&page->lru, &tmp_list); > + page++; > + } > } > + > + list_splice(&tmp_list, list); > } > > static inline bool migrate_async_suitable(int migratetype) > @@ -368,12 +386,13 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > unsigned long flags = 0; > bool locked = false; > unsigned long blockpfn = *start_pfn; > + unsigned int order; > > cursor = pfn_to_page(blockpfn); > > /* Isolate free pages. */ > for (; blockpfn < end_pfn; blockpfn++, cursor++) { > - int isolated, i; > + int isolated; > struct page *page = cursor; > > /* > @@ -439,13 +458,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > goto isolate_fail; > } > > - /* Found a free page, break it into order-0 pages */ > - isolated = split_free_page(page); > + /* Found a free page, will break it into order-0 pages */ > + order = page_order(page); > + isolated = __isolate_free_page(page, page_order(page)); > + set_page_private(page, order); > total_isolated += isolated; > - for (i = 0; i < isolated; i++) { > - list_add(&page->lru, freelist); > - page++; > - } > + list_add_tail(&page->lru, freelist); > > /* If a page was split, advance to the end of it */ > if (isolated) { > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5dd65d9..60d7f10 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2532,33 +2532,6 @@ int __isolate_free_page(struct page *page, unsigned int order) > } > > /* > - * Similar to split_page except the page is already free. As this is only > - * being used for migration, the migratetype of the block also changes. > - * As this is called with interrupts disabled, the caller is responsible > - * for calling arch_alloc_page() and kernel_map_page() after interrupts > - * are enabled. > - * > - * Note: this is probably too low level an operation for use in drivers. > - * Please consult with lkml before using this in your driver. > - */ > -int split_free_page(struct page *page) > -{ > - unsigned int order; > - int nr_pages; > - > - order = page_order(page); > - > - nr_pages = __isolate_free_page(page, order); > - if (!nr_pages) > - return 0; > - > - /* Split into individual pages */ > - set_page_refcounted(page); > - split_page(page, order); > - return nr_pages; > -} > - > -/* > * Update NUMA hit/miss statistics > * > * Must be called with interrupts disabled. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>