On Thu, Apr 15, 2010 at 07:24:53PM +0900, KOSAKI Motohiro wrote: > Now, vmscan is using __pagevec_free() for batch freeing. but > pagevec consume slightly lots stack (sizeof(long)*8), and x86_64 > stack is very strictly limited. > > Then, now we are planning to use page->lru list instead pagevec > for reducing stack. and introduce new helper function. > > This is similar to __pagevec_free(), but receive list instead > pagevec. and this don't use pcp cache. it is good characteristics > for vmscan. > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > --- > include/linux/gfp.h | 1 + > mm/page_alloc.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 45 insertions(+), 0 deletions(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index 4c6d413..dbcac56 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -332,6 +332,7 @@ extern void free_hot_cold_page(struct page *page, int cold); > #define __free_page(page) __free_pages((page), 0) > #define free_page(addr) free_pages((addr),0) > > +void free_pages_bulk(struct zone *zone, struct list_head *list); > void page_alloc_init(void); > void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp); > void drain_all_pages(void); > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ba9aea7..1f68832 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2049,6 +2049,50 @@ void free_pages(unsigned long addr, unsigned int order) > > EXPORT_SYMBOL(free_pages); > > +/* > + * Frees a number of pages from the list > + * Assumes all pages on list are in same zone and order==0. > + * > + * This is similar to __pagevec_free(), but receive list instead pagevec. > + * and this don't use pcp cache. it is good characteristics for vmscan. > + */ > +void free_pages_bulk(struct zone *zone, struct list_head *list) > +{ > + unsigned long flags; > + struct page *page; > + struct page *page2; > + int nr_pages = 0; > + > + list_for_each_entry_safe(page, page2, list, lru) { > + int wasMlocked = __TestClearPageMlocked(page); > + > + if (free_pages_prepare(page, 0)) { > + /* Make orphan the corrupted page. */ > + list_del(&page->lru); > + continue; > + } > + if (unlikely(wasMlocked)) { > + local_irq_save(flags); > + free_page_mlock(page); > + local_irq_restore(flags); > + } You could clear this under the zone->lock below before calling __free_one_page. It'd avoid a large number of IRQ enables and disables which are a problem on some CPUs (P4 and Itanium both blow in this regard according to PeterZ). > + nr_pages++; > + } > + > + spin_lock_irqsave(&zone->lock, flags); > + __count_vm_events(PGFREE, nr_pages); > + zone->all_unreclaimable = 0; > + zone->pages_scanned = 0; > + __mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages); > + > + list_for_each_entry_safe(page, page2, list, lru) { > + /* have to delete it as __free_one_page list manipulates */ > + list_del(&page->lru); > + __free_one_page(page, zone, 0, page_private(page)); > + } This has the effect of bypassing the per-cpu lists as well as making the zone lock hotter. The cache hotness of the data within the page is probably not a factor but the cache hotness of the stuct page is. The zone lock getting hotter is a greater problem. Large amounts of page reclaim or dumping of page cache will now contend on the zone lock where as previously it would have dumped into the per-cpu lists (potentially but not necessarily avoiding the zone lock). While there might be a stack saving in the next patch, there would appear to be definite performance implications in taking this patch. Functionally, I see no problem but I'd put this sort of patch on the very long finger until the performance aspects of it could be examined. > + spin_unlock_irqrestore(&zone->lock, flags); > +} > + > /** > * alloc_pages_exact - allocate an exact number physically-contiguous pages. > * @size: the number of bytes to allocate > -- > 1.6.5.2 > > > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html