From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 5C2036B038B for ; Thu, 16 Mar 2017 02:31:46 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id g2so74972282pge.7 for ; Wed, 15 Mar 2017 23:31:46 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id o1si4304418pld.248.2017.03.15.23.31.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Mar 2017 23:31:45 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH -mm -v6 3/9] mm, THP, swap: Add swap cluster allocate/free functions References: <20170308072613.17634-1-ying.huang@intel.com> <20170308072613.17634-4-ying.huang@intel.com> <1489533213.2733.33.camel@linux.intel.com> <87wpbrcp5s.fsf@yhuang-dev.intel.com> <1489598142.2733.60.camel@linux.intel.com> Date: Thu, 16 Mar 2017 14:31:40 +0800 In-Reply-To: <1489598142.2733.60.camel@linux.intel.com> (Tim Chen's message of "Wed, 15 Mar 2017 10:15:42 -0700") Message-ID: <87bmt1yboz.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Tim Chen Cc: "Huang, Ying" , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrea Arcangeli , "Kirill A . Shutemov" , Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel Tim Chen writes: > On Wed, 2017-03-15 at 09:19 +0800, Huang, Ying wrote: >> Tim Chen writes: >> >> > >> > On Wed, 2017-03-08 at 15:26 +0800, Huang, Ying wrote: >> > > >> > > From: Huang Ying >> > > >> > > The swap cluster allocation/free functions are added based on the >> > > existing swap cluster management mechanism for SSD.A A These functions >> > > don't work for the rotating hard disks because the existing swap cluster >> > > management mechanism doesn't work for them.A A The hard disks support may >> > > be added if someone really need it.A A But that needn't be included in >> > > this patchset. >> > > >> > > This will be used for the THP (Transparent Huge Page) swap support. >> > > Where one swap cluster will hold the contents of each THP swapped out. >> > > >> > > Cc: Andrea Arcangeli >> > > Cc: Kirill A. Shutemov >> > > Cc: Hugh Dickins >> > > Cc: Shaohua Li >> > > Cc: Minchan Kim >> > > Cc: Rik van Riel >> > > Signed-off-by: "Huang, Ying" >> > > --- >> > > A mm/swapfile.c | 217 +++++++++++++++++++++++++++++++++++++++++----------------- >> > > A 1 file changed, 156 insertions(+), 61 deletions(-) >> > > >> > > diff --git a/mm/swapfile.c b/mm/swapfile.c >> > > index a744604384ff..91876c33114b 100644 >> > > --- a/mm/swapfile.c >> > > +++ b/mm/swapfile.c >> > > @@ -378,6 +378,14 @@ static void swap_cluster_schedule_discard(struct swap_info_struct *si, >> > > A schedule_work(&si->discard_work); >> > > A } >> > > A >> > > +static void __free_cluster(struct swap_info_struct *si, unsigned long idx) >> > > +{ >> > > + struct swap_cluster_info *ci = si->cluster_info; >> > > + >> > > + cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE); >> > > + cluster_list_add_tail(&si->free_clusters, ci, idx); >> > > +} >> > > + >> > > A /* >> > > A * Doing discard actually. After a cluster discard is finished, the cluster >> > > A * will be added to free cluster list. caller should hold si->lock. >> > > @@ -398,10 +406,7 @@ static void swap_do_scheduled_discard(struct swap_info_struct *si) >> > > A >> > > A spin_lock(&si->lock); >> > > A ci = lock_cluster(si, idx * SWAPFILE_CLUSTER); >> > > - cluster_set_flag(ci, CLUSTER_FLAG_FREE); >> > > - unlock_cluster(ci); >> > > - cluster_list_add_tail(&si->free_clusters, info, idx); >> > > - ci = lock_cluster(si, idx * SWAPFILE_CLUSTER); >> > > + __free_cluster(si, idx); >> > > A memset(si->swap_map + idx * SWAPFILE_CLUSTER, >> > > A 0, SWAPFILE_CLUSTER); >> > > A unlock_cluster(ci); >> > The __free_cluster definition and the above change to eliminate >> > the extra unlock_cluster and lock_cluster can perhaps be broken up >> > as a separate patch. A It can be independent of THP changes. >> I think the change may have no value by itself without THP changes. >> There will be only 1 user of __free_cluster() and the lock change is >> trivial too.A A So I think it may be better just to keep it as that? >> > > Seems like the extra unlock and lock of cluster in existing code should be taken out > irrespective of the THP changes: > A > cluster_set_flag(ci, CLUSTER_FLAG_FREE); > - unlock_cluster(ci); > cluster_list_add_tail(&si->free_clusters, info, idx); > - ci = lock_cluster(si, idx * SWAPFILE_CLUSTER); > memset(si->swap_map + idx * SWAPFILE_CLUSTER, > A A 0, SWAPFILE_CLUSTER); > This is not a functionality fix or performance optimization. Because the lock on the swap_info_struct is held during the operation and there are no operations on cluster with index "idx" in cluster_list_add_tail(). The change here is just to make the resulting code a little simpler. Is this deserved a separate patch? Best Regards, Huang, Ying -- 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