Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932599AbcCMJ3p (ORCPT ); Sun, 13 Mar 2016 05:29:45 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:37394 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932293AbcCMJ3Q (ORCPT ); Sun, 13 Mar 2016 05:29:16 -0400 From: Ebru Akagunduz To: linux-mm@kvack.org Cc: hughd@google.com, riel@redhat.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, iamjoonsoo.kim@lge.com, gorcunov@openvz.org, linux-kernel@vger.kernel.org, mgorman@suse.de, rientjes@google.com, vbabka@suse.cz, aneesh.kumar@linux.vnet.ibm.com, hannes@cmpxchg.org, mhocko@suse.cz, boaz@plexistor.com, Ebru Akagunduz Subject: [PATCH v2 2/2] mm, thp: avoid unnecessary swapin in khugepaged Date: Sun, 13 Mar 2016 11:28:55 +0200 Message-Id: <1457861335-23297-3-git-send-email-ebru.akagunduz@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1457861335-23297-1-git-send-email-ebru.akagunduz@gmail.com> References: <1457861335-23297-1-git-send-email-ebru.akagunduz@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3723 Lines: 92 Currently khugepaged makes swapin readahead to improve THP collapse rate. This patch checks vm statistics to avoid workload of swapin, if unnecessary. So that when system under pressure, khugepaged won't consume resources to swapin. The patch was tested with a test program that allocates 800MB of memory, writes to it, and then sleeps. The system was forced to swap out all. Afterwards, the test program touches the area by writing, it skips a page in each 20 pages of the area. When waiting to swapin readahead left part of the test, the memory forced to be busy doing page reclaim. There was enough free memory during test, khugepaged did not swapin readahead due to business. Test results: After swapped out ------------------------------------------------------------------- | Anonymous | AnonHugePages | Swap | Fraction | ------------------------------------------------------------------- With patch | 325784 kB | 325632 kB | 474216 kB | %99 | ------------------------------------------------------------------- Without patch | 351308 kB | 350208 kB | 448692 kB | %99 | ------------------------------------------------------------------- After swapped in (waiting 10 minutes) ------------------------------------------------------------------- | Anonymous | AnonHugePages | Swap | Fraction | ------------------------------------------------------------------- With patch | 714164 kB | 489472 kB | 85836 kB | %68 | ------------------------------------------------------------------- Without patch | 586816 kB | 464896 kB | 213184 kB | %79 | ------------------------------------------------------------------- Signed-off-by: Ebru Akagunduz Fixes: 363cd76e5b11c ("mm: make swapin readahead to improve thp collapse rate") --- Changes in v2: - Add reference to specify which patch fixed (Ebru Akagunduz) - Fix commit subject line (Ebru Akagunduz) mm/huge_memory.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 86e9666..4a60035 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -102,6 +102,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); */ static unsigned int khugepaged_max_ptes_none __read_mostly; static unsigned int khugepaged_max_ptes_swap __read_mostly; +static unsigned long int allocstall = 0; static int khugepaged(void *none); static int khugepaged_slab_init(void); @@ -2438,7 +2439,7 @@ static void collapse_huge_page(struct mm_struct *mm, struct page *new_page; spinlock_t *pmd_ptl, *pte_ptl; int isolated = 0, result = 0; - unsigned long hstart, hend; + unsigned long hstart, hend, swap = 0, curr_allocstall = 0; struct mem_cgroup *memcg; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ @@ -2493,7 +2494,14 @@ static void collapse_huge_page(struct mm_struct *mm, goto out; } - __collapse_huge_page_swapin(mm, vma, address, pmd); + swap = get_mm_counter(mm, MM_SWAPENTS); + curr_allocstall = sum_vm_event(ALLOCSTALL); + /* + * When system under pressure, don't swapin readahead. + * So that avoid unnecessary resource consuming. + */ + if (allocstall == curr_allocstall && swap != 0) + __collapse_huge_page_swapin(mm, vma, address, pmd); anon_vma_lock_write(vma->anon_vma); @@ -2790,6 +2798,7 @@ skip: VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); + allocstall = sum_vm_event(ALLOCSTALL); ret = khugepaged_scan_pmd(mm, vma, khugepaged_scan.address, hpage); -- 1.9.1