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From:   Zi Yan <zi.yan@sent.com>
To:     Dave Hansen <dave.hansen@linux.intel.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Keith Busch <keith.busch@intel.com>,
        Fengguang Wu <fengguang.wu@intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Daniel Jordan <daniel.m.jordan@oracle.com>,
        Michal Hocko <mhocko@kernel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>,
        John Hubbard <jhubbard@nvidia.com>,
        Mark Hairgrove <mhairgrove@nvidia.com>,
        Nitin Gupta <nigupta@nvidia.com>,
        Javier Cabezas <jcabezas@nvidia.com>,
        David Nellans <dnellans@nvidia.com>, Zi Yan <ziy@nvidia.com>
Subject: [RFC PATCH 05/25] mm: migrate: Add vm.accel_page_copy in sysfs to control page copy acceleration.
Date:   Wed,  3 Apr 2019 19:00:26 -0700
Message-Id: <20190404020046.32741-6-zi.yan@sent.com>
In-Reply-To: <20190404020046.32741-1-zi.yan@sent.com>
References: <20190404020046.32741-1-zi.yan@sent.com>
Reply-To: ziy@nvidia.com
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From: Zi Yan <ziy@nvidia.com>

Since base page migration did not gain any speedup from
multi-threaded methods, we only accelerate the huge page case.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 kernel/sysctl.c | 11 +++++++++++
 mm/migrate.c    |  6 ++++++
 2 files changed, 17 insertions(+)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e5da394..3d8490e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -101,6 +101,8 @@
 
 #if defined(CONFIG_SYSCTL)
 
+extern int accel_page_copy;
+
 /* External variables not in a header file. */
 extern int suid_dumpable;
 #ifdef CONFIG_COREDUMP
@@ -1430,6 +1432,15 @@ static struct ctl_table vm_table[] = {
 		.extra2			= &one,
 	},
 #endif
+	{
+		.procname	= "accel_page_copy",
+		.data		= &accel_page_copy,
+		.maxlen		= sizeof(accel_page_copy),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &zero,
+		.extra2		= &one,
+	},
 	 {
 		.procname	= "hugetlb_shm_group",
 		.data		= &sysctl_hugetlb_shm_group,
diff --git a/mm/migrate.c b/mm/migrate.c
index dd6ccbe..8a344e2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -55,6 +55,8 @@
 
 #include "internal.h"
 
+int accel_page_copy = 1;
+
 /*
  * migrate_prep() needs to be called before we start compiling a list of pages
  * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
@@ -589,6 +591,10 @@ static void copy_huge_page(struct page *dst, struct page *src,
 		nr_pages = hpage_nr_pages(src);
 	}
 
+	/* Try to accelerate page migration if it is not specified in mode  */
+	if (accel_page_copy)
+		mode |= MIGRATE_MT;
+
 	if (mode & MIGRATE_MT)
 		rc = copy_page_multithread(dst, src, nr_pages);
 
-- 
2.7.4