From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967157AbdDZUOG (ORCPT ); Wed, 26 Apr 2017 16:14:06 -0400 Received: from mga14.intel.com ([192.55.52.115]:5688 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936362AbdDZUN7 (ORCPT ); Wed, 26 Apr 2017 16:13:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,255,1488873600"; d="scan'208";a="79299444" Message-ID: <1493237623.3209.142.camel@linux.intel.com> Subject: Re: [PATCH -mm -v3] mm, swap: Sort swap entries before free From: Tim Chen To: "Huang, Ying" , Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Shaohua Li , Rik van Riel Date: Wed, 26 Apr 2017 13:13:43 -0700 In-Reply-To: <87y3un2vdp.fsf@yhuang-dev.intel.com> References: <20170407064901.25398-1-ying.huang@intel.com> <20170418045909.GA11015@bbox> <87y3uwrez0.fsf@yhuang-dev.intel.com> <20170420063834.GB3720@bbox> <874lxjim7m.fsf@yhuang-dev.intel.com> <87tw5idjv9.fsf@yhuang-dev.intel.com> <20170424045213.GA11287@bbox> <87y3un2vdp.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 > > From 7bd903c42749c448ef6acbbdee8dcbc1c5b498b9 Mon Sep 17 00:00:00 2001 > From: Huang Ying > Date: Thu, 23 Feb 2017 13:05:20 +0800 > Subject: [PATCH -v5] mm, swap: Sort swap entries before free > >  > --- >  mm/swapfile.c | 43 ++++++++++++++++++++++++++++++++++++++----- >  1 file changed, 38 insertions(+), 5 deletions(-) > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 71890061f653..10e75f9e8ac1 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -37,6 +37,7 @@ >  #include >  #include >  #include > +#include >   >  #include >  #include > @@ -1065,20 +1066,52 @@ void swapcache_free(swp_entry_t entry) >   } >  } >   > +static int swp_entry_cmp(const void *ent1, const void *ent2) > +{ > + const swp_entry_t *e1 = ent1, *e2 = ent2; > + > + return (int)(swp_type(*e1) - swp_type(*e2)); > +} > + >  void swapcache_free_entries(swp_entry_t *entries, int n) >  { >   struct swap_info_struct *p, *prev; > - int i; > + int i, m; > + swp_entry_t entry; > + unsigned int prev_swp_type; I think it will be clearer to name prev_swp_type as first_swp_type as this is the swp type of the first entry. >   >   if (n <= 0) >   return; >   >   prev = NULL; >   p = NULL; > - for (i = 0; i < n; ++i) { > - p = swap_info_get_cont(entries[i], prev); > - if (p) > - swap_entry_free(p, entries[i]); > + m = 0; > + prev_swp_type = swp_type(entries[0]); > + for (i = 0; i < n; i++) { > + entry = entries[i]; > + if (likely(swp_type(entry) == prev_swp_type)) { > + p = swap_info_get_cont(entry, prev); > + if (likely(p)) > + swap_entry_free(p, entry); > + prev = p; > + } else if (!m) > + m = i; > + } > + if (p) > + spin_unlock(&p->lock); > + if (likely(!m)) > + return; > + We could still have prev_swp_type at the first entry after sorting. and we can avoid an unlock/relock for this case if we do this: if (likely(!m)) { if (p) spin_unlock(&p->lock); return; } > + /* Sort swap entries by swap device, so each lock is only taken once. */ > + sort(entries + m, n - m, sizeof(entries[0]), swp_entry_cmp, NULL); > + prev = NULL; Can eliminate prev=NULL if we adopt the above change. > + for (i = m; i < n; i++) { > + entry = entries[i]; > + if (swp_type(entry) == prev_swp_type) > + continue; The if/continue statement seems incorrect. When swp_type(entry) == prev_swp_type we also need to free entry.  The if/continue statement should be deleted. Say we have 3 entries with swp_type 1,2,1 We will get prev_swp_type as 1 and free the first entry and sort the remaining two.  The last entry with swp_type 1 will not be freed. > + p = swap_info_get_cont(entry, prev); > + if (likely(p)) > + swap_entry_free(p, entry); >   prev = p; >   } >   if (p) Thanks. Tim From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 001CF6B02F2 for ; Wed, 26 Apr 2017 16:13:46 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id p2so6468041pge.7 for ; Wed, 26 Apr 2017 13:13:45 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id 2si319266pla.216.2017.04.26.13.13.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Apr 2017 13:13:44 -0700 (PDT) Message-ID: <1493237623.3209.142.camel@linux.intel.com> Subject: Re: [PATCH -mm -v3] mm, swap: Sort swap entries before free From: Tim Chen Date: Wed, 26 Apr 2017 13:13:43 -0700 In-Reply-To: <87y3un2vdp.fsf@yhuang-dev.intel.com> References: <20170407064901.25398-1-ying.huang@intel.com> <20170418045909.GA11015@bbox> <87y3uwrez0.fsf@yhuang-dev.intel.com> <20170420063834.GB3720@bbox> <874lxjim7m.fsf@yhuang-dev.intel.com> <87tw5idjv9.fsf@yhuang-dev.intel.com> <20170424045213.GA11287@bbox> <87y3un2vdp.fsf@yhuang-dev.intel.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" , Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Shaohua Li , Rik van Riel > > From 7bd903c42749c448ef6acbbdee8dcbc1c5b498b9 Mon Sep 17 00:00:00 2001 > From: Huang Ying > Date: Thu, 23 Feb 2017 13:05:20 +0800 > Subject: [PATCH -v5] mm, swap: Sort swap entries before free > >A > --- > A mm/swapfile.c | 43 ++++++++++++++++++++++++++++++++++++++----- > A 1 file changed, 38 insertions(+), 5 deletions(-) > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 71890061f653..10e75f9e8ac1 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -37,6 +37,7 @@ > A #include > A #include > A #include > +#include > A > A #include > A #include > @@ -1065,20 +1066,52 @@ void swapcache_free(swp_entry_t entry) > A } > A } > A > +static int swp_entry_cmp(const void *ent1, const void *ent2) > +{ > + const swp_entry_t *e1 = ent1, *e2 = ent2; > + > + return (int)(swp_type(*e1) - swp_type(*e2)); > +} > + > A void swapcache_free_entries(swp_entry_t *entries, int n) > A { > A struct swap_info_struct *p, *prev; > - int i; > + int i, m; > + swp_entry_t entry; > + unsigned int prev_swp_type; I think it will be clearer to name prev_swp_type as first_swp_type as this is the swp type of the first entry. > A > A if (n <= 0) > A return; > A > A prev = NULL; > A p = NULL; > - for (i = 0; i < n; ++i) { > - p = swap_info_get_cont(entries[i], prev); > - if (p) > - swap_entry_free(p, entries[i]); > + m = 0; > + prev_swp_type = swp_type(entries[0]); > + for (i = 0; i < n; i++) { > + entry = entries[i]; > + if (likely(swp_type(entry) == prev_swp_type)) { > + p = swap_info_get_cont(entry, prev); > + if (likely(p)) > + swap_entry_free(p, entry); > + prev = p; > + } else if (!m) > + m = i; > + } > + if (p) > + spin_unlock(&p->lock); > + if (likely(!m)) > + return; > + We could still have prev_swp_type at the first entry after sorting. and we can avoid an unlock/relock for this case if we do this: if (likely(!m)) { if (p) spin_unlock(&p->lock); return; } > + /* Sort swap entries by swap device, so each lock is only taken once. */ > + sort(entries + m, n - m, sizeof(entries[0]), swp_entry_cmp, NULL); > + prev = NULL; Can eliminate prev=NULL if we adopt the above change. > + for (i = m; i < n; i++) { > + entry = entries[i]; > + if (swp_type(entry) == prev_swp_type) > + continue; The if/continue statement seems incorrect. When swp_type(entry) == prev_swp_type we also need to free entry. A The if/continue statement should be deleted. Say we have 3 entries with swp_type 1,2,1 We will get prev_swp_type as 1 and free the first entry and sort the remaining two. A The last entry with swp_type 1 will not be freed. > + p = swap_info_get_cont(entry, prev); > + if (likely(p)) > + swap_entry_free(p, entry); > A prev = p; > A } > A if (p) Thanks. Tim -- 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