linux-kernel - [PATCH 2/3] mm/util.c: make vm_memory

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Message-Id: <1588922717-63697-3-git-send-email-feng.tang@intel.com>
Date:   Fri,  8 May 2020 15:25:16 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Kees Cook <keescook@...omium.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>, andi.kleen@...el.com,
        tim.c.chen@...el.com, dave.hansen@...el.com, ying.huang@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Feng Tang <feng.tang@...el.com>
Subject: [PATCH 2/3] mm/util.c: make vm_memory_committed() more accurate

percpu_counter_sum_positive() will provide more accurate info.

Its time cost is about 800 nanoseconds on a 2C/4T platform and
2~3 microseconds on a 2S/36C/72T server in normal case, and in
worst case where vm_committed_as's spinlock is under severe
contention, it costs 30~40 microseconds for the 2S/36C/72T sever,
which should be fine for its two users: /proc/meminfo and HV ballon
driver's status trace per second.

Signed-off-by: Feng Tang <feng.tang@...el.com>
---
 mm/util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/util.c b/mm/util.c
index 988d11e..3de78e9 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -774,7 +774,7 @@ struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
  */
 unsigned long vm_memory_committed(void)
 {
-	return percpu_counter_read_positive(&vm_committed_as);
+	return percpu_counter_sum_positive(&vm_committed_as);
 }
 EXPORT_SYMBOL_GPL(vm_memory_committed);
 
-- 
2.7.4