linux-kernel - [PATCH v4 11/26] mm/mips: Use general page fault accounting

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Message-Id: <20200630204530.39003-1-peterx@redhat.com>
Date:   Tue, 30 Jun 2020 16:45:30 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        John Hubbard <jhubbard@...dia.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org
Subject: [PATCH v4 11/26] mm/mips: Use general page fault accounting

Use the general page fault accounting by passing regs into handle_mm_fault().
It naturally solve the issue of multiple page fault accounting when page fault
retry happened.

Fix PERF_COUNT_SW_PAGE_FAULTS perf event manually for page fault retries, by
moving it before taking mmap_sem.

CC: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
CC: linux-mips@...r.kernel.org
Acked-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/mips/mm/fault.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index b1db39784db9..7c871b14e74a 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -96,6 +96,8 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
 
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
 	mmap_read_lock(mm);
 	vma = find_vma(mm, address);
@@ -152,12 +154,11 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	fault = handle_mm_fault(vma, address, flags, NULL);
+	fault = handle_mm_fault(vma, address, flags, regs);
 
 	if (fault_signal_pending(fault, regs))
 		return;
 
-	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)
 			goto out_of_memory;
@@ -168,15 +169,6 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
 		BUG();
 	}
 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
-		if (fault & VM_FAULT_MAJOR) {
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-						  regs, address);
-			tsk->maj_flt++;
-		} else {
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-						  regs, address);
-			tsk->min_flt++;
-		}
 		if (fault & VM_FAULT_RETRY) {
 			flags |= FAULT_FLAG_TRIED;
 
-- 
2.26.2