From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753425AbdCORRi (ORCPT ); Wed, 15 Mar 2017 13:17:38 -0400 Received: from mga01.intel.com ([192.55.52.88]:47426 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752939AbdCORQF (ORCPT ); Wed, 15 Mar 2017 13:16:05 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,169,1486454400"; d="scan'208";a="1108805012" Message-ID: <1489598142.2733.60.camel@linux.intel.com> Subject: Re: [PATCH -mm -v6 3/9] mm, THP, swap: Add swap cluster allocate/free functions From: Tim Chen To: "Huang, Ying" Cc: 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 Date: Wed, 15 Mar 2017 10:15:42 -0700 In-Reply-To: <87wpbrcp5s.fsf@yhuang-dev.intel.com> 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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2 (3.18.5.2-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.  These functions > > > don't work for the rotating hard disks because the existing swap cluster > > > management mechanism doesn't work for them.  The hard disks support may > > > be added if someone really need it.  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" > > > --- > > >  mm/swapfile.c | 217 +++++++++++++++++++++++++++++++++++++++++----------------- > > >  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, > > >   schedule_work(&si->discard_work); > > >  } > > >   > > > +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); > > > +} > > > + > > >  /* > > >   * Doing discard actually. After a cluster discard is finished, the cluster > > >   * 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) > > >   > > >   spin_lock(&si->lock); > > >   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); > > >   memset(si->swap_map + idx * SWAPFILE_CLUSTER, > > >   0, SWAPFILE_CLUSTER); > > >   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.  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.  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:   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,    0, SWAPFILE_CLUSTER); Tim