Messages in this thread Patch in this message | | | Date | Mon, 14 Jan 2019 19:29:39 +0530 | From | Arun KS <> | Subject | Re: [PATCH v9] mm/page_alloc.c: memory_hotplug: free pages as higher order |
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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@codeaurora.org> >> Acked-by: Michal Hocko <mhocko@suse.com> >> Reviewed-by: Oscar Salvador <osalvador@suse.de> > > 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@linux.intel.com> > >> --- >> 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
> >> + (*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); >> } >> } >>
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