Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754147AbcCIV4T (ORCPT ); Wed, 9 Mar 2016 16:56:19 -0500 Received: from mail-wm0-f47.google.com ([74.125.82.47]:35887 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753094AbcCIV4F (ORCPT ); Wed, 9 Mar 2016 16:56:05 -0500 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] mm: avoid unnecessary swapin in khugepaged Date: Wed, 9 Mar 2016 23:55:43 +0200 Message-Id: <1457560543-15910-1-git-send-email-ebru.akagunduz@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3725 Lines: 96 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 | 450964 kB | 450560 kB | 349036 kB | %99 | ------------------------------------------------------------------- Without patch | 351308 kB | 350208 kB | 448692 kB | %99 | ------------------------------------------------------------------- After swapped in (waiting 10 minutes) ------------------------------------------------------------------- | Anonymous | AnonHugePages | Swap | Fraction | ------------------------------------------------------------------- With patch | 637932 kB | 559104 kB | 162068 kB | %69 | ------------------------------------------------------------------- Without patch | 586816 kB | 464896 kB | 213184 kB | %79 | ------------------------------------------------------------------- Signed-off-by: Ebru Akagunduz --- mm/huge_memory.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7f75292..109a2af 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); @@ -2411,6 +2412,7 @@ static void collapse_huge_page(struct mm_struct *mm, struct mem_cgroup *memcg; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ + unsigned long events[NR_VM_EVENT_ITEMS], swap = 0; gfp_t gfp; VM_BUG_ON(address & ~HPAGE_PMD_MASK); @@ -2463,7 +2465,15 @@ static void collapse_huge_page(struct mm_struct *mm, goto out; } - __collapse_huge_page_swapin(mm, vma, address, pmd); + all_vm_events(events); + swap = get_mm_counter(mm, MM_SWAPENTS); + + /* + * When system under pressure, don't swapin readahead. + * So that avoid unnecessary resource consuming. + */ + if (allocstall == events[ALLOCSTALL] && swap != 0) + __collapse_huge_page_swapin(mm, vma, address, pmd); anon_vma_lock_write(vma->anon_vma); @@ -2706,6 +2716,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, struct mm_struct *mm; struct vm_area_struct *vma; int progress = 0; + unsigned long events[NR_VM_EVENT_ITEMS]; VM_BUG_ON(!pages); VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); @@ -2760,6 +2771,8 @@ skip: VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); + all_vm_events(events); + allocstall = events[ALLOCSTALL]; ret = khugepaged_scan_pmd(mm, vma, khugepaged_scan.address, hpage); -- 1.9.1