From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751017AbdCOAOY (ORCPT ); Tue, 14 Mar 2017 20:14:24 -0400 Received: from mga09.intel.com ([134.134.136.24]:23829 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbdCOAOW (ORCPT ); Tue, 14 Mar 2017 20:14:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,166,1486454400"; d="scan'208";a="67445937" Message-ID: <1489536859.2733.53.camel@linux.intel.com> Subject: Re: [PATCH -mm -v6 5/9] mm, THP, swap: Support to clear SWAP_HAS_CACHE for huge page From: Tim Chen To: "Huang, Ying" , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrea Arcangeli , "Kirill A . Shutemov" , Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel Date: Tue, 14 Mar 2017 17:14:19 -0700 In-Reply-To: <20170308072613.17634-6-ying.huang@intel.com> References: <20170308072613.17634-1-ying.huang@intel.com> <20170308072613.17634-6-ying.huang@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, 2017-03-08 at 15:26 +0800, Huang, Ying wrote: > From: Huang Ying > > __swapcache_free() is added to support to clear the SWAP_HAS_CACHE flag > for the huge page.  This will free the specified swap cluster now. > Because now this function will be called only in the error path to free > the swap cluster just allocated.  So the corresponding swap_map[i] == > SWAP_HAS_CACHE, that is, the swap count is 0.  This makes the > implementation simpler than that of the ordinary swap entry. > > This will be used for delaying splitting THP (Transparent Huge Page) > during swapping out.  Where for one THP to swap out, we will allocate a > swap cluster, add the THP into the swap cache, then split the THP.  If > anything fails after allocating the swap cluster and before splitting > the THP successfully, the swapcache_free_trans_huge() will be used to > free the swap space allocated. > > 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" > --- >  include/linux/swap.h |  9 +++++++-- >  mm/swapfile.c        | 34 ++++++++++++++++++++++++++++++++-- >  2 files changed, 39 insertions(+), 4 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index e3a7609a8989..2f2a6c0363aa 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -394,7 +394,7 @@ extern void swap_shmem_alloc(swp_entry_t); >  extern int swap_duplicate(swp_entry_t); >  extern int swapcache_prepare(swp_entry_t); >  extern void swap_free(swp_entry_t); > -extern void swapcache_free(swp_entry_t); > +extern void __swapcache_free(swp_entry_t entry, bool huge); >  extern void swapcache_free_entries(swp_entry_t *entries, int n); >  extern int free_swap_and_cache(swp_entry_t); >  extern int swap_type_of(dev_t, sector_t, struct block_device **); > @@ -456,7 +456,7 @@ static inline void swap_free(swp_entry_t swp) >  { >  } >   > -static inline void swapcache_free(swp_entry_t swp) > +static inline void __swapcache_free(swp_entry_t swp, bool huge) >  { >  } >   > @@ -544,6 +544,11 @@ static inline swp_entry_t get_huge_swap_page(void) >  } >  #endif >   > +static inline void swapcache_free(swp_entry_t entry) > +{ > + __swapcache_free(entry, false); > +} > + >  #ifdef CONFIG_MEMCG >  static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) >  { > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 7241c937e52b..6019f94afbaf 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -855,6 +855,29 @@ static void swap_free_huge_cluster(struct swap_info_struct *si, >   _swap_entry_free(si, offset, true); >  } >   > +static void swapcache_free_trans_huge(struct swap_info_struct *si, > +       swp_entry_t entry) > +{ > + unsigned long offset = swp_offset(entry); > + unsigned long idx = offset / SWAPFILE_CLUSTER; > + struct swap_cluster_info *ci; > + unsigned char *map; > + unsigned int i; > + > + spin_lock(&si->lock); > + ci = lock_cluster(si, offset); > + map = si->swap_map + offset; > + for (i = 0; i < SWAPFILE_CLUSTER; i++) { > + VM_BUG_ON(map[i] != SWAP_HAS_CACHE); > + map[i] &= ~SWAP_HAS_CACHE; Nitpicking a bit: map[i] = 0  is more readable if map[i] == SWAP_HAS_CACHE here. Thanks. Tim