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Date: Mon, 10 Sep 2018 16:43:48 -0700 From: Alexander Duyck <alexander.duyck@...il.com> To: linux-mm@...ck.org, linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org Cc: pavel.tatashin@...rosoft.com, mhocko@...e.com, dave.jiang@...el.com, mingo@...nel.org, dave.hansen@...el.com, jglisse@...hat.com, akpm@...ux-foundation.org, logang@...tatee.com, dan.j.williams@...el.com, kirill.shutemov@...ux.intel.com Subject: [PATCH 2/4] mm: Create non-atomic version of SetPageReserved for init use From: Alexander Duyck <alexander.h.duyck@...el.com> It doesn't make much sense to use the atomic SetPageReserved at init time when we are using memset to clear the memory and manipulating the page flags via simple "&=" and "|=" operations in __init_single_page. This patch adds a non-atomic version __SetPageReserved that can be used during page init and shows about a 10% improvement in initialization times on the systems I have available for testing. On those systems I saw initialization times drop from around 35 seconds to around 32 seconds to initialize a 3TB block of persistent memory. I tried adding a bit of documentation based on commit <f1dd2cd13c4> ("mm, memory_hotplug: do not associate hotadded memory to zones until online"). Ideally the reserved flag should be set earlier since there is a brief window where the page is initialization via __init_single_page and we have not set the PG_Reserved flag. I'm leaving that for a future patch set as that will require a more significant refactor. Acked-by: Michal Hocko <mhocko@...e.com> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com> --- include/linux/page-flags.h | 1 + mm/page_alloc.c | 17 +++++++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index d00216cf00f8..1b1f8e0378ae 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -300,6 +300,7 @@ static inline void page_init_poison(struct page *page, size_t size) PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND) __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND) + __SETPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND) PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL) __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL) __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 89d2a2ab3fe6..a9b095a72fd9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1231,7 +1231,12 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end) /* Avoid false-positive PageTail() */ INIT_LIST_HEAD(&page->lru); - SetPageReserved(page); + /* + * no need for atomic set_bit because the struct + * page is not visible yet so nobody should + * access it yet. + */ + __SetPageReserved(page); } } } @@ -5517,8 +5522,16 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, not_early: page = pfn_to_page(pfn); __init_single_page(page, pfn, zone, nid); + + /* + * Mark page reserved as it will need to wait for onlining + * phase for it to be fully associated with a zone. + * + * We can use the non-atomic __set_bit operation for setting + * the flag as we are still initializing the pages. + */ if (context == MEMMAP_HOTPLUG) - SetPageReserved(page); + __SetPageReserved(page); /* * Mark the block movable so that blocks are reserved for
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