From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx199.postini.com [74.125.245.199]) by kanga.kvack.org (Postfix) with SMTP id D74836B002B for ; Fri, 24 Aug 2012 10:38:13 -0400 (EDT) Received: from /spool/local by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 25 Aug 2012 00:36:56 +1000 Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q7OEc9XB25624700 for ; Sat, 25 Aug 2012 00:38:09 +1000 Received: from d23av02.au.ibm.com (loopback [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q7OEc8Jg023372 for ; Sat, 25 Aug 2012 00:38:08 +1000 From: Wanpeng Li Subject: [PATCH 1/2] mm/mmu_notifier: init notifier if necessary Date: Fri, 24 Aug 2012 22:37:55 +0800 Message-Id: <1345819076-12545-1-git-send-email-liwanp@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Michal Hocko , KAMEZAWA Hiroyuki , Minchan Kim , Andrew Morton , Gavin Shan , Wanpeng Li From: Gavin Shan While registering MMU notifier, new instance of MMU notifier_mm will be allocated and later free'd if currrent mm_struct's MMU notifier_mm has been initialized. That cause some overhead. The patch tries to eleminate that. Signed-off-by: Gavin Shan Signed-off-by: Wanpeng Li --- mm/mmu_notifier.c | 22 +++++++++++----------- 1 files changed, 11 insertions(+), 11 deletions(-) diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index 862b608..fb4067f 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -192,22 +192,23 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, BUG_ON(atomic_read(&mm->mm_users) <= 0); - ret = -ENOMEM; - mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); - if (unlikely(!mmu_notifier_mm)) - goto out; - if (take_mmap_sem) down_write(&mm->mmap_sem); ret = mm_take_all_locks(mm); if (unlikely(ret)) - goto out_cleanup; + goto out; if (!mm_has_notifiers(mm)) { + mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), + GFP_ATOMIC); + if (unlikely(!mmu_notifier_mm)) { + ret = -ENOMEM; + goto out_of_mem; + } INIT_HLIST_HEAD(&mmu_notifier_mm->list); spin_lock_init(&mmu_notifier_mm->lock); + mm->mmu_notifier_mm = mmu_notifier_mm; - mmu_notifier_mm = NULL; } atomic_inc(&mm->mm_count); @@ -223,13 +224,12 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list); spin_unlock(&mm->mmu_notifier_mm->lock); +out_of_mem: mm_drop_all_locks(mm); -out_cleanup: +out: if (take_mmap_sem) up_write(&mm->mmap_sem); - /* kfree() does nothing if mmu_notifier_mm is NULL */ - kfree(mmu_notifier_mm); -out: + BUG_ON(atomic_read(&mm->mm_users) <= 0); return ret; } -- 1.7.7.6 -- 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