| Message ID | 1492076108-117229-4-git-send-email-wei.w.wang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 13 Apr 2017 17:35:06 +0800 Wei Wang <wei.w.wang@intel.com> wrote: > Add a function to find a page block on the free list specified by the > caller. Pages from the page block may be used immediately after the > function returns. The caller is responsible for detecting or preventing > the use of such pages. > > ... > > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4498,6 +4498,93 @@ void show_free_areas(unsigned int filter) > show_swap_cache_info(); > } > > +/** > + * Heuristically get a page block in the system that is unused. > + * It is possible that pages from the page block are used immediately after > + * inquire_unused_page_block() returns. It is the caller's responsibility > + * to either detect or prevent the use of such pages. > + * > + * The free list to check: zone->free_area[order].free_list[migratetype]. > + * > + * If the caller supplied page block (i.e. **page) is on the free list, offer > + * the next page block on the list to the caller. Otherwise, offer the first > + * page block on the list. > + * > + * Return 0 when a page block is found on the caller specified free list. > + */ > +int inquire_unused_page_block(struct zone *zone, unsigned int order, > + unsigned int migratetype, struct page **page) > +{ Perhaps we can wrap this in the appropriate ifdef so the kernels which won't be using virtio-balloon don't carry the added overhead.
On 04/14/2017 04:02 AM, Andrew Morton wrote: > On Thu, 13 Apr 2017 17:35:06 +0800 Wei Wang <wei.w.wang@intel.com> wrote: > >> Add a function to find a page block on the free list specified by the >> caller. Pages from the page block may be used immediately after the >> function returns. The caller is responsible for detecting or preventing >> the use of such pages. >> >> ... >> >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -4498,6 +4498,93 @@ void show_free_areas(unsigned int filter) >> show_swap_cache_info(); >> } >> >> +/** >> + * Heuristically get a page block in the system that is unused. >> + * It is possible that pages from the page block are used immediately after >> + * inquire_unused_page_block() returns. It is the caller's responsibility >> + * to either detect or prevent the use of such pages. >> + * >> + * The free list to check: zone->free_area[order].free_list[migratetype]. >> + * >> + * If the caller supplied page block (i.e. **page) is on the free list, offer >> + * the next page block on the list to the caller. Otherwise, offer the first >> + * page block on the list. >> + * >> + * Return 0 when a page block is found on the caller specified free list. >> + */ >> +int inquire_unused_page_block(struct zone *zone, unsigned int order, >> + unsigned int migratetype, struct page **page) >> +{ > Perhaps we can wrap this in the appropriate ifdef so the kernels which > won't be using virtio-balloon don't carry the added overhead. > > OK. What do you think if we add this: #if defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE) Best, Wei
On Fri, Apr 14, 2017 at 10:30:27AM +0800, Wei Wang wrote: > OK. What do you think if we add this: > > #if defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE) That's spelled "IS_ENABLED(CONFIG_VIRTIO_BALLOON)", FYI.
On 04/14/2017 10:58 AM, Matthew Wilcox wrote: > On Fri, Apr 14, 2017 at 10:30:27AM +0800, Wei Wang wrote: >> OK. What do you think if we add this: >> >> #if defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE) > That's spelled "IS_ENABLED(CONFIG_VIRTIO_BALLOON)", FYI. Right, thanks. Best, Wei
diff --git a/include/linux/mm.h b/include/linux/mm.h index b84615b..096705e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1764,6 +1764,9 @@ extern void free_area_init(unsigned long * zones_size); extern void free_area_init_node(int nid, unsigned long * zones_size, unsigned long zone_start_pfn, unsigned long *zholes_size); extern void free_initmem(void); +extern int inquire_unused_page_block(struct zone *zone, unsigned int order, + unsigned int migratetype, + struct page **page); /* * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f3e0c69..fa8203f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4498,6 +4498,93 @@ void show_free_areas(unsigned int filter) show_swap_cache_info(); } +/** + * Heuristically get a page block in the system that is unused. + * It is possible that pages from the page block are used immediately after + * inquire_unused_page_block() returns. It is the caller's responsibility + * to either detect or prevent the use of such pages. + * + * The free list to check: zone->free_area[order].free_list[migratetype]. + * + * If the caller supplied page block (i.e. **page) is on the free list, offer + * the next page block on the list to the caller. Otherwise, offer the first + * page block on the list. + * + * Return 0 when a page block is found on the caller specified free list. + */ +int inquire_unused_page_block(struct zone *zone, unsigned int order, + unsigned int migratetype, struct page **page) +{ + struct zone *this_zone; + struct list_head *this_list; + int ret = 0; + unsigned long flags; + + /* Sanity check */ + if (zone == NULL || page == NULL || order >= MAX_ORDER || + migratetype >= MIGRATE_TYPES) + return -EINVAL; + + /* Zone validity check */ + for_each_populated_zone(this_zone) { + if (zone == this_zone) + break; + } + + /* Got a non-existent zone from the caller? */ + if (zone != this_zone) + return -EINVAL; + + spin_lock_irqsave(&this_zone->lock, flags); + + this_list = &zone->free_area[order].free_list[migratetype]; + if (list_empty(this_list)) { + *page = NULL; + ret = 1; + goto out; + } + + /* The caller is asking for the first free page block on the list */ + if ((*page) == NULL) { + *page = list_first_entry(this_list, struct page, lru); + ret = 0; + goto out; + } + + /** + * The page block passed from the caller is not on this free list + * anymore (e.g. a 1MB free page block has been split). In this case, + * offer the first page block on the free list that the caller is + * asking for. + */ + if (PageBuddy(*page) && order != page_order(*page)) { + *page = list_first_entry(this_list, struct page, lru); + ret = 0; + goto out; + } + + /** + * The page block passed from the caller has been the last page block + * on the list. + */ + if ((*page)->lru.next == this_list) { + *page = NULL; + ret = 1; + goto out; + } + + /** + * Finally, fall into the regular case: the page block passed from the + * caller is still on the free list. Offer the next one. + */ + *page = list_next_entry((*page), lru); + ret = 0; +out: + spin_unlock_irqrestore(&this_zone->lock, flags); + return ret; +} +EXPORT_SYMBOL(inquire_unused_page_block); + static void zoneref_set_zone(struct zone *zone, struct zoneref *zoneref) { zoneref->zone = zone;