From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751220AbdCOAyv (ORCPT ); Tue, 14 Mar 2017 20:54:51 -0400 Received: from mga11.intel.com ([192.55.52.93]:39969 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521AbdCOAys (ORCPT ); Tue, 14 Mar 2017 20:54:48 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,166,1486454400"; d="scan'208";a="1142340990" From: "Huang\, Ying" To: Tim Chen Cc: "Huang\, Ying" , Andrew Morton , , , Andrea Arcangeli , "Kirill A . Shutemov" , Hugh Dickins , "Shaohua Li" , Minchan Kim , Rik van Riel Subject: Re: [PATCH -mm -v6 5/9] mm, THP, swap: Support to clear SWAP_HAS_CACHE for huge page References: <20170308072613.17634-1-ying.huang@intel.com> <20170308072613.17634-6-ying.huang@intel.com> <1489536859.2733.53.camel@linux.intel.com> Date: Wed, 15 Mar 2017 08:54:44 +0800 In-Reply-To: <1489536859.2733.53.camel@linux.intel.com> (Tim Chen's message of "Tue, 14 Mar 2017 17:14:19 -0700") Message-ID: <87a88ne4vf.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tim Chen writes: > 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. OK. I will change this. Best Regards, Huang, Ying