On Mon, 2019-01-14 at 19:29 +0530, Arun KS wrote: > On 2019-01-10 21:53, Alexander Duyck wrote: > > 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. > > Good catch. I ll change the check to, > if ((pfn < has->start_pfn) || > (pfn + (1UL << order) >= 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); > > > 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. > > Thanks for that. How about this? > > static int online_pages_blocks(unsigned long start, unsigned long > nr_pages) > { > unsigned long end = start + nr_pages; > int order; > > while (nr_pages) { > if (nr_pages >= (1UL << (MAX_ORDER - 1))) > order = MAX_ORDER - 1; > else > order = __fls(nr_pages); > > (*online_page_callback)(pfn_to_page(start), order); > nr_pages -= (1UL << order); > start += (1UL << order); > } > return end - start; > } > > Regards, > Arun You would still need to return onlined_pages or something similar at the end of the function. The problem is end - start should always be 0 if your loop succeeds. Either that or you could save of nr_pages to onlined_pages directly and then return that and the end of the function.
