When free pages are done with higher order, time spend on coalescing pages by buddy allocator can be reduced. With section size of 256MB, hot add latency of a single section shows improvement from 50-60 ms to less than 1 ms, hence improving the hot add latency by 60%. Modify external providers of online callback to align with the change. Signed-off-by: Arun KS <arunks@xxxxxxxxxxxxxx> --- Changes since RFC: - Rebase. - As suggested by Michal Hocko remove pages_per_block. - Modifed external providers of online_page_callback. RFC: https://lore.kernel.org/patchwork/patch/984754/ --- drivers/hv/hv_balloon.c | 6 +++-- drivers/xen/balloon.c | 18 +++++++++++--- include/linux/memory_hotplug.h | 2 +- mm/memory_hotplug.c | 55 +++++++++++++++++++++++++++++++++--------- 4 files changed, 63 insertions(+), 18 deletions(-) diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index b1b7880..c5bc0b5 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -771,7 +771,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size, } } -static void hv_online_page(struct page *pg) +static int hv_online_page(struct page *pg, unsigned int order) { struct hv_hotadd_state *has; unsigned long flags; @@ -783,10 +783,12 @@ static void hv_online_page(struct page *pg) if ((pfn < has->start_pfn) || (pfn >= has->end_pfn)) continue; - hv_page_online_one(has, pg); + hv_bring_pgs_online(has, pfn, (1UL << order)); break; } spin_unlock_irqrestore(&dm_device.ha_lock, flags); + + return 0; } static int pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index e12bb25..010cf4d 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -390,8 +390,8 @@ static enum bp_state reserve_additional_memory(void) /* * add_memory_resource() will call online_pages() which in its turn - * will call xen_online_page() callback causing deadlock if we don't - * release balloon_mutex here. Unlocking here is safe because the + * will call xen_bring_pgs_online() callback causing deadlock if we + * don't release balloon_mutex here. Unlocking here is safe because the * callers drop the mutex before trying again. */ mutex_unlock(&balloon_mutex); @@ -422,6 +422,18 @@ static void xen_online_page(struct page *page) mutex_unlock(&balloon_mutex); } +static int xen_bring_pgs_online(struct page *pg, unsigned int order) +{ + unsigned long i, size = (1 << order); + unsigned long start_pfn = page_to_pfn(pg); + + pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn); + for (i = 0; i < size; i++) + xen_online_page(pfn_to_page(start_pfn + i)); + + return 0; +} + static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v) { if (val == MEM_ONLINE) @@ -744,7 +756,7 @@ static int __init balloon_init(void) balloon_stats.max_retry_count = RETRY_UNLIMITED; #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG - set_online_page_callback(&xen_online_page); + set_online_page_callback(&xen_bring_pgs_online); register_memory_notifier(&xen_memory_nb); register_sysctl_table(xen_root); diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 34a2822..7b04c1d 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -87,7 +87,7 @@ extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn, unsigned long *valid_start, unsigned long *valid_end); extern void __offline_isolated_pages(unsigned long, unsigned long); -typedef void (*online_page_callback_t)(struct page *page); +typedef int (*online_page_callback_t)(struct page *page, unsigned int order); extern int set_online_page_callback(online_page_callback_t callback); extern int restore_online_page_callback(online_page_callback_t callback); diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 38d94b7..24c2b8e 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -47,7 +47,7 @@ * and restore_online_page_callback() for generic callback restore. */ -static void generic_online_page(struct page *page); +static int generic_online_page(struct page *page, unsigned int order); static online_page_callback_t online_page_callback = generic_online_page; static DEFINE_MUTEX(online_page_callback_lock); @@ -655,26 +655,57 @@ void __online_page_free(struct page *page) } EXPORT_SYMBOL_GPL(__online_page_free); -static void generic_online_page(struct page *page) +static int generic_online_page(struct page *page, unsigned int order) { - __online_page_set_limits(page); - __online_page_increment_counters(page); - __online_page_free(page); + unsigned long nr_pages = 1 << order; + struct page *p = page; + unsigned int loop; + + prefetchw(p); + for (loop = 0 ; loop < (nr_pages - 1) ; loop++, p++) { + prefetch(p + 1); + __ClearPageReserved(p); + set_page_count(p, 0); + } + __ClearPageReserved(p); + set_page_count(p, 0); + + adjust_managed_page_count(page, nr_pages); + set_page_refcounted(page); + __free_pages(page, order); + + return 0; +} + +static int online_pages_blocks(unsigned long start, unsigned long nr_pages) +{ + unsigned long end = start + nr_pages; + int order, ret, onlined_pages = 0; + + while (start < end) { + order = min(MAX_ORDER - 1UL, __ffs(start)); + + while (start + (1UL << order) > end) + order--; + + ret = (*online_page_callback)(pfn_to_page(start), order); + if (!ret) + onlined_pages += (1UL << order); + else if (ret > 0) + onlined_pages += ret; + + start += (1UL << order); + } + return onlined_pages; } static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, void *arg) { - unsigned long i; unsigned long onlined_pages = *(unsigned long *)arg; - struct page *page; if (PageReserved(pfn_to_page(start_pfn))) - for (i = 0; i < nr_pages; i++) { - page = pfn_to_page(start_pfn + i); - (*online_page_callback)(page); - onlined_pages++; - } + onlined_pages = online_pages_blocks(start_pfn, nr_pages); online_mem_sections(start_pfn, start_pfn + nr_pages); -- 1.9.1
