[PATCH v12 30/31] arm64/mm: add speculative page fault

From: Laurent Dufour <ldufour@linux.ibm.com>
To: akpm@linux-foundation.org, mhocko@kernel.org,
	peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com,
	dave@stgolabs.net, jack@suse.cz,
	Matthew Wilcox <willy@infradead.org>,
	aneesh.kumar@linux.ibm.com, benh@kernel.crashing.org,
	mpe@ellerman.id.au, paulus@samba.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	hpa@zytor.com, Will Deacon <will.deacon@arm.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	sergey.senozhatsky.work@gmail.com,
	Andrea Arcangeli <aarcange@redhat.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	kemi.wang@intel.com, Daniel Jordan <daniel.m.jordan@oracle.com>,
	David Rientjes <rientjes@google.com>,
	Jerome Glisse <jglisse@redhat.com>,
	Ganesh Mahendran <opensource.ganesh@gmail.com>,
	Minchan Kim <minchan@kernel.org>,
	Punit Agrawal <punitagrawal@gmail.com>,
	vinayak menon <vinayakm.list@gmail.com>,
	Yang Shi <yang.shi@linux.alibaba.com>,
	zhong jiang <zhongjiang@huawei.com>,
	Haiyan Song <haiyanx.song@intel.com>,
	Balbir Singh <bsingharora@gmail.com>,
	sj38.park@gmail.com, Michel Lespinasse <walken@google.com>,
	Mike Rapoport <rppt@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	haren@linux.vnet.ibm.com, npiggin@gmail.com,
	paulmck@linux.vnet.ibm.com, Tim Chen <tim.c.chen@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: [PATCH v12 30/31] arm64/mm: add speculative page fault
Date: Tue, 16 Apr 2019 15:45:21 +0200	[thread overview]
Message-ID: <20190416134522.17540-31-ldufour@linux.ibm.com> (raw)
In-Reply-To: <20190416134522.17540-1-ldufour@linux.ibm.com>

From: Mahendran Ganesh <opensource.ganesh@gmail.com>

This patch enables the speculative page fault on the arm64
architecture.

I completed spf porting in 4.9. From the test result,
we can see app launching time improved by about 10% in average.
For the apps which have more than 50 threads, 15% or even more
improvement can be got.

Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>

[handle_speculative_fault() is no more returning the vma pointer]
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
 arch/arm64/mm/fault.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 4f343e603925..b5e2a93f9c21 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -485,6 +485,16 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
+	/*
+	 * let's try a speculative page fault without grabbing the
+	 * mmap_sem.
+	 */
+	fault = handle_speculative_fault(mm, addr, mm_flags);
+	if (fault != VM_FAULT_RETRY) {
+		perf_sw_event(PERF_COUNT_SW_SPF, 1, regs, addr);
+		goto done;
+	}
+
 	/*
 	 * As per x86, we may deadlock here. However, since the kernel only
 	 * validly references user space from well defined areas of the code,
@@ -535,6 +545,8 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 	}
 	up_read(&mm->mmap_sem);
 
+done:
+
 	/*
 	 * Handle the "normal" (no error) case first.
 	 */
-- 
2.21.0

