On Thu, 2019-01-10 at 11:05 +0530, Arun KS wrote: > When freeing pages are done with higher order, time spent 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 times. Modify > external providers of online callback to align with the change. > > Signed-off-by: Arun KS <arunks@xxxxxxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> So I decided to give this one last thorough review and I think I might have found a few more minor issues, but not anything that is necessarily a showstopper. Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> > --- > Changes since v8: > - Remove return type change for online_page_callback. > - Use consistent names for external online_page providers. > - Fix onlined_pages accounting. > > Changes since v7: > - Rebased to 5.0-rc1. > - Fixed onlined_pages accounting. > - Added comment for return value of online_page_callback. > - Renamed xen_bring_pgs_online to xen_online_pages. > > Changes since v6: > - Rebased to 4.20 > - Changelog updated. > - No improvement seen on arm64, hence removed removal of prefetch. > > Changes since v5: > - Rebased to 4.20-rc1. > - Changelog updated. > > Changes since v4: > - As suggested by Michal Hocko, > - Simplify logic in online_pages_block() by using get_order(). > - Seperate out removal of prefetch from __free_pages_core(). > > Changes since v3: > - Renamed _free_pages_boot_core -> __free_pages_core. > - Removed prefetch from __free_pages_core. > - Removed xen_online_page(). > > Changes since v2: > - Reuse code from __free_pages_boot_core(). > > Changes since v1: > - Removed prefetch(). > > Changes since RFC: > - Rebase. > - As suggested by Michal Hocko remove pages_per_block. > - Modifed external providers of online_page_callback. > > v8: https://lore.kernel.org/patchwork/patch/1030332/ > v7: https://lore.kernel.org/patchwork/patch/1028908/ > v6: https://lore.kernel.org/patchwork/patch/1007253/ > v5: https://lore.kernel.org/patchwork/patch/995739/ > v4: https://lore.kernel.org/patchwork/patch/995111/ > v3: https://lore.kernel.org/patchwork/patch/992348/ > v2: https://lore.kernel.org/patchwork/patch/991363/ > v1: https://lore.kernel.org/patchwork/patch/989445/ > RFC: https://lore.kernel.org/patchwork/patch/984754/ > --- > --- > drivers/hv/hv_balloon.c | 4 ++-- > drivers/xen/balloon.c | 15 ++++++++++----- > include/linux/memory_hotplug.h | 2 +- > mm/internal.h | 1 + > mm/memory_hotplug.c | 37 +++++++++++++++++++++++++------------ > mm/page_alloc.c | 8 ++++---- > 6 files changed, 43 insertions(+), 24 deletions(-) > > diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c > index 5301fef..55d79f8 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 void hv_online_page(struct page *pg, unsigned int order) > { > struct hv_hotadd_state *has; > unsigned long flags; > @@ -783,7 +783,7 @@ static void hv_online_page(struct page *pg) > if ((pfn < has->start_pfn) || (pfn >= has->end_pfn)) > continue; > I haven't followed earlier reviews, but do we know for certain the entire range being onlined will fit within a single hv_hotadd_state? If nothing else it seems like this check should be updated so that we are checking to verify that pfn + (1UL << order) is less than or equal to has->end_pfn. > - hv_page_online_one(has, pg); > + hv_bring_pgs_online(has, pfn, (1UL << order)); > break; > } > spin_unlock_irqrestore(&dm_device.ha_lock, flags); > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index ceb5048..d107447 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -369,14 +369,19 @@ static enum bp_state reserve_additional_memory(void) > return BP_ECANCELED; > } > > -static void xen_online_page(struct page *page) > +static void xen_online_page(struct page *page, unsigned int order) > { > - __online_page_set_limits(page); > + unsigned long i, size = (1 << order); > + unsigned long start_pfn = page_to_pfn(page); > + struct page *p; > > + pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn); > mutex_lock(&balloon_mutex); > - > - __balloon_append(page); > - > + for (i = 0; i < size; i++) { > + p = pfn_to_page(start_pfn + i); > + __online_page_set_limits(p); > + __balloon_append(p); > + } > mutex_unlock(&balloon_mutex); > } > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index 07da5c6..e368730 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 void (*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/internal.h b/mm/internal.h > index f4a7bb0..536bc2a 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -163,6 +163,7 @@ static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn, > extern int __isolate_free_page(struct page *page, unsigned int order); > extern void memblock_free_pages(struct page *page, unsigned long pfn, > unsigned int order); > +extern void __free_pages_core(struct page *page, unsigned int order); > extern void prep_compound_page(struct page *page, unsigned int order); > extern void post_alloc_hook(struct page *page, unsigned int order, > gfp_t gfp_flags); > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index b9a667d..77dff24 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 void 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); > @@ -656,26 +656,39 @@ void __online_page_free(struct page *page) > } > EXPORT_SYMBOL_GPL(__online_page_free); > > -static void generic_online_page(struct page *page) > +static void generic_online_page(struct page *page, unsigned int order) > { > - __online_page_set_limits(page); > - __online_page_increment_counters(page); > - __online_page_free(page); > + __free_pages_core(page, order); > + totalram_pages_add(1UL << order); > +#ifdef CONFIG_HIGHMEM > + if (PageHighMem(page)) > + totalhigh_pages_add(1UL << order); > +#endif > +} > + > +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 - 1, > + get_order(PFN_PHYS(end) - PFN_PHYS(start))); So this is mostly just optimization related so you can ignore this suggestion if you want. I was looking at this and it occurred to me that I don't think you need to convert this to a physical address do you? Couldn't you just do something like the following: if ((end - start) >= (1UL << (MAX_ORDER - 1)) order = MAX_ORDER - 1; else order = __fls(end - start); I would think this would save you a few steps in terms of conversions and such since you are already working in page frame numbers anyway so a block of 8 pfns would represent an order 3 page wouldn't it? Also it seems like an alternative to using "end" would be to just track nr_pages. Then you wouldn't have to do the "end - start" math in a few spots as long as you remembered to decrement nr_pages by the amount you increment start by. > + (*online_page_callback)(pfn_to_page(start), order); > + > + onlined_pages += (1UL << order); > + 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); > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d295c9b..883212a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1303,7 +1303,7 @@ static void __free_pages_ok(struct page *page, unsigned int order) > local_irq_restore(flags); > } > > -static void __init __free_pages_boot_core(struct page *page, unsigned int order) > +void __free_pages_core(struct page *page, unsigned int order) > { > unsigned int nr_pages = 1 << order; > struct page *p = page; > @@ -1382,7 +1382,7 @@ void __init memblock_free_pages(struct page *page, unsigned long pfn, > { > if (early_page_uninitialised(pfn)) > return; > - return __free_pages_boot_core(page, order); > + __free_pages_core(page, order); > } > > /* > @@ -1472,14 +1472,14 @@ static void __init deferred_free_range(unsigned long pfn, > if (nr_pages == pageblock_nr_pages && > (pfn & (pageblock_nr_pages - 1)) == 0) { > set_pageblock_migratetype(page, MIGRATE_MOVABLE); > - __free_pages_boot_core(page, pageblock_order); > + __free_pages_core(page, pageblock_order); > return; > } > > for (i = 0; i < nr_pages; i++, page++, pfn++) { > if ((pfn & (pageblock_nr_pages - 1)) == 0) > set_pageblock_migratetype(page, MIGRATE_MOVABLE); > - __free_pages_boot_core(page, 0); > + __free_pages_core(page, 0); > } > } >
