linux-kernel - [PATCH] perf: Make the mlock accounting simple again

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Message-Id: <20191120170640.54123-1-alexander.shishkin@linux.intel.com>
Date:   Wed, 20 Nov 2019 19:06:40 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        songliubraving@...com
Subject: [PATCH] perf: Make the mlock accounting simple again

Commit

  d44248a41337 ("perf/core: Rework memory accounting in perf_mmap()")

does a lot of things to the mlock accounting arithmetics, while the only
thing that actually needed to happen is subtracting the part that is
charged to the mm from the part that is charged to the user, so that the
former isn't charged twice.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: songliubraving@...com
---
 kernel/events/core.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 522438887206..059ee7116008 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5886,13 +5886,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
 	user_locked = atomic_long_read(&user->locked_vm) + user_extra;
 
-	if (user_locked <= user_lock_limit) {
-		/* charge all to locked_vm */
-	} else if (atomic_long_read(&user->locked_vm) >= user_lock_limit) {
-		/* charge all to pinned_vm */
-		extra = user_extra;
-		user_extra = 0;
-	} else {
+	if (user_locked > user_lock_limit) {
 		/*
 		 * charge locked_vm until it hits user_lock_limit;
 		 * charge the rest from pinned_vm
-- 
2.24.0