From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f52.google.com (mail-pb0-f52.google.com [209.85.160.52]) by kanga.kvack.org (Postfix) with ESMTP id 38A9A6B0035 for ; Thu, 29 May 2014 02:19:35 -0400 (EDT) Received: by mail-pb0-f52.google.com with SMTP id rr13so12442023pbb.25 for ; Wed, 28 May 2014 23:19:34 -0700 (PDT) Received: from lgeamrelo04.lge.com (lgeamrelo04.lge.com. [156.147.1.127]) by mx.google.com with ESMTP id sl5si26970584pab.202.2014.05.28.23.19.32 for ; Wed, 28 May 2014 23:19:34 -0700 (PDT) From: Joonsoo Kim Subject: [PATCH] vmalloc: use rcu list iterator to reduce vmap_area_lock contention Date: Thu, 29 May 2014 15:22:34 +0900 Message-Id: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Zhang Yanfei , Johannes Weiner , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Richard Yao , Joonsoo Kim Richard Yao reported a month ago that his system have a trouble with vmap_area_lock contention during performance analysis by /proc/meminfo. Andrew asked why his analysis checks /proc/meminfo stressfully, but he didn't answer it. https://lkml.org/lkml/2014/4/10/416 Although I'm not sure that this is right usage or not, there is a solution reducing vmap_area_lock contention with no side-effect. That is just to use rcu list iterator in get_vmalloc_info(). This function only needs values on vmap_area structure, so we don't need to grab a spinlock. Reported-by: Richard Yao Signed-off-by: Joonsoo Kim diff --git a/mm/vmalloc.c b/mm/vmalloc.c index f64632b..fdbb116 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2690,14 +2690,14 @@ void get_vmalloc_info(struct vmalloc_info *vmi) prev_end = VMALLOC_START; - spin_lock(&vmap_area_lock); + rcu_read_lock(); if (list_empty(&vmap_area_list)) { vmi->largest_chunk = VMALLOC_TOTAL; goto out; } - list_for_each_entry(va, &vmap_area_list, list) { + list_for_each_entry_rcu(va, &vmap_area_list, list) { unsigned long addr = va->va_start; /* @@ -2724,7 +2724,7 @@ void get_vmalloc_info(struct vmalloc_info *vmi) vmi->largest_chunk = VMALLOC_END - prev_end; out: - spin_unlock(&vmap_area_lock); + rcu_read_unlock(); } #endif -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org