From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id E265B6B03A3 for ; Wed, 5 Apr 2017 03:10:53 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id 197so2565839pfv.13 for ; Wed, 05 Apr 2017 00:10:53 -0700 (PDT) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id d76si19807043pfe.306.2017.04.05.00.10.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 05 Apr 2017 00:10:53 -0700 (PDT) From: "Huang, Ying" Subject: [PATCH -mm -v2] mm, swap: Sort swap entries before free Date: Wed, 5 Apr 2017 15:10:41 +0800 Message-Id: <20170405071041.24469-1-ying.huang@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel From: Huang Ying To reduce the lock contention of swap_info_struct->lock when freeing swap entry. The freed swap entries will be collected in a per-CPU buffer firstly, and be really freed later in batch. During the batch freeing, if the consecutive swap entries in the per-CPU buffer belongs to same swap device, the swap_info_struct->lock needs to be acquired/released only once, so that the lock contention could be reduced greatly. But if there are multiple swap devices, it is possible that the lock may be unnecessarily released/acquired because the swap entries belong to the same swap device are non-consecutive in the per-CPU buffer. To solve the issue, the per-CPU buffer is sorted according to the swap device before freeing the swap entries. Test shows that the time spent by swapcache_free_entries() could be reduced after the patch. Test the patch via measuring the run time of swap_cache_free_entries() during the exit phase of the applications use much swap space. The results shows that the average run time of swap_cache_free_entries() reduced about 20% after applying the patch. Signed-off-by: Huang Ying Acked-by: Tim Chen Cc: Hugh Dickins Cc: Shaohua Li Cc: Minchan Kim Cc: Rik van Riel v2: - Avoid sort swap entries if there is only one swap device. --- mm/swapfile.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/swapfile.c b/mm/swapfile.c index 90054f3c2cdc..b91b0b0088c5 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -1065,6 +1066,13 @@ 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 (long)(swp_type(*e1) - swp_type(*e2)); +} + void swapcache_free_entries(swp_entry_t *entries, int n) { struct swap_info_struct *p, *prev; @@ -1075,6 +1083,8 @@ void swapcache_free_entries(swp_entry_t *entries, int n) prev = NULL; p = NULL; + if (nr_swapfiles > 1) + sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL); for (i = 0; i < n; ++i) { p = swap_info_get_cont(entries[i], prev); if (p) -- 2.11.0 -- 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