From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) by kanga.kvack.org (Postfix) with ESMTP id BFD768E0001 for ; Thu, 20 Sep 2018 18:27:57 -0400 (EDT) Received: by mail-pg1-f199.google.com with SMTP id v186-v6so3668312pgb.14 for ; Thu, 20 Sep 2018 15:27:57 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id p7-v6si24646254plo.159.2018.09.20.15.27.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Sep 2018 15:27:56 -0700 (PDT) Subject: [PATCH v4 2/5] mm: Create non-atomic version of SetPageReserved for init use From: Alexander Duyck Date: Thu, 20 Sep 2018 15:27:53 -0700 Message-ID: <20180920222641.19464.75787.stgit@localhost.localdomain> In-Reply-To: <20180920215824.19464.8884.stgit@localhost.localdomain> References: <20180920215824.19464.8884.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org Cc: pavel.tatashin@microsoft.com, mhocko@suse.com, dave.jiang@intel.com, mingo@kernel.org, dave.hansen@intel.com, jglisse@redhat.com, akpm@linux-foundation.org, logang@deltatee.com, dan.j.williams@intel.com, kirill.shutemov@linux.intel.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 believe the main advantage of this is that it allows for more compiler optimization as the __set_bit operation can be reordered whereas the atomic version cannot. I tried adding a bit of documentation based on commit ("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 Signed-off-by: Alexander Duyck --- v4: Added comment about __set_bit vs set_bit to the patch description include/linux/page-flags.h | 1 + mm/page_alloc.c | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 934f91ef3f54..50ce1bddaf56 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -303,6 +303,7 @@ 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 712cab17f86f..29bd662fffd7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1239,7 +1239,12 @@ 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); } } } @@ -5513,7 +5518,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, page = pfn_to_page(pfn); __init_single_page(page, pfn, zone, nid); if (context == MEMMAP_HOTPLUG) - SetPageReserved(page); + __SetPageReserved(page); /* * Mark the block movable so that blocks are reserved for