Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932889Ab2HXOhb (ORCPT ); Fri, 24 Aug 2012 10:37:31 -0400 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:55660 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932488Ab2HXOh1 (ORCPT ); Fri, 24 Aug 2012 10:37:27 -0400 From: Wanpeng Li To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Michal Hocko , KAMEZAWA Hiroyuki , Minchan Kim , Andrew Morton , Gavin Shan , Wanpeng Li Subject: [PATCH 1/2] mm/mmu_notifier: init notifier if necessary Date: Fri, 24 Aug 2012 22:37:04 +0800 Message-Id: <1345819025-12445-1-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 x-cbid: 12082414-5490-0000-0000-00000204560F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2107 Lines: 73 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/