Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751959AbcCNVkd (ORCPT ); Mon, 14 Mar 2016 17:40:33 -0400 Received: from mail-wm0-f44.google.com ([74.125.82.44]:33693 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbcCNVka (ORCPT ); Mon, 14 Mar 2016 17:40:30 -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 v3 2/2] mm, thp: avoid unnecessary swapin in khugepaged Date: Mon, 14 Mar 2016 23:40:11 +0200 Message-Id: <1457991611-6211-3-git-send-email-ebru.akagunduz@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1457991611-6211-1-git-send-email-ebru.akagunduz@gmail.com> References: <1457991611-6211-1-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: 3707 Lines: 94 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 | 206608 kB | 204800 kB | 593392 kB | %99 | ------------------------------------------------------------------- Without patch | 351308 kB | 350208 kB | 448692 kB | %99 | ------------------------------------------------------------------- After swapped in (waiting 10 minutes) ------------------------------------------------------------------- | Anonymous | AnonHugePages | Swap | Fraction | ------------------------------------------------------------------- With patch | 551992 kB | 368640 kB | 248008 kB | %66 | ------------------------------------------------------------------- Without patch | 586816 kB | 464896 kB | 213184 kB | %79 | ------------------------------------------------------------------- Signed-off-by: Ebru Akagunduz --- Changes in v2: - Add reference to specify which patch fixed (Ebru Akagunduz) - Fix commit subject line (Ebru Akagunduz) Changes in v3: - Remove default values of allocstall (Kirill A. Shutemov) 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..67a398c 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; 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, curr_allocstall; 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