From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michael Kerrisk <mtk.manpages@gmail.com>,
linux-api@vger.kernel.org, Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Jason Evans <je@fb.com>, Daniel Micay <danielmicay@gmail.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Shaohua Li <shli@kernel.org>, Michal Hocko <mhocko@suse.cz>,
yalin.wang2010@gmail.com, Andy Lutomirski <luto@amacapital.net>,
Minchan Kim <minchan@kernel.org>, Michal Hocko <mhocko@suse.com>
Subject: [PATCH v5 04/12] mm: free swp_entry in madvise_free
Date: Mon, 30 Nov 2015 15:39:35 +0900 [thread overview]
Message-ID: <1448865583-2446-5-git-send-email-minchan@kernel.org> (raw)
In-Reply-To: <1448865583-2446-1-git-send-email-minchan@kernel.org>
When I test below piece of code with 12 processes(ie, 512M * 12 = 6G
consume) on my (3G ram + 12 cpu + 8G swap, the madvise_free is siginficat
slower (ie, 2x times) than madvise_dontneed.
loop = 5;
mmap(512M);
while (loop--) {
memset(512M);
madvise(MADV_FREE or MADV_DONTNEED);
}
The reason is lots of swapin.
1) dontneed: 1,612 swapin
2) madvfree: 879,585 swapin
If we find hinted pages were already swapped out when syscall is called,
it's pointless to keep the swapped-out pages in pte.
Instead, let's free the cold page because swapin is more expensive
than (alloc page + zeroing).
With this patch, it reduced swapin from 879,585 to 1,878 so elapsed time
1) dontneed: 6.10user 233.50system 0:50.44elapsed
2) madvfree: 6.03user 401.17system 1:30.67elapsed
2) madvfree + below patch: 6.70user 339.14system 1:04.45elapsed
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/madvise.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index e2fe2e26f449..8de3d9a636c9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -270,6 +270,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
spinlock_t *ptl;
pte_t *orig_pte, *pte, ptent;
struct page *page;
+ int nr_swap = 0;
split_huge_pmd(vma, pmd, addr);
if (pmd_trans_unstable(pmd))
@@ -280,8 +281,24 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
for (; addr != end; pte++, addr += PAGE_SIZE) {
ptent = *pte;
- if (!pte_present(ptent))
+ if (pte_none(ptent))
continue;
+ /*
+ * If the pte has swp_entry, just clear page table to
+ * prevent swap-in which is more expensive rather than
+ * (page allocation + zeroing).
+ */
+ if (!pte_present(ptent)) {
+ swp_entry_t entry;
+
+ entry = pte_to_swp_entry(ptent);
+ if (non_swap_entry(entry))
+ continue;
+ nr_swap--;
+ free_swap_and_cache(entry);
+ pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
+ continue;
+ }
page = vm_normal_page(vma, addr, ptent);
if (!page)
@@ -353,6 +370,12 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
}
}
out:
+ if (nr_swap) {
+ if (current->mm == mm)
+ sync_mm_rss(mm);
+
+ add_mm_counter(mm, MM_SWAPENTS, nr_swap);
+ }
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(orig_pte, ptl);
cond_resched();
--
1.9.1
next prev parent reply other threads:[~2015-11-30 6:39 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-30 6:39 [PATCH v5 00/12] MADV_FREE support Minchan Kim
2015-11-30 6:39 ` [PATCH v5 01/12] mm: support madvise(MADV_FREE) Minchan Kim
2015-11-30 8:20 ` Mika Penttilä
2015-11-30 9:22 ` Minchan Kim
2015-11-30 6:39 ` [PATCH v5 02/12] mm: define MADV_FREE for some arches Minchan Kim
2015-11-30 6:39 ` [PATCH v5 03/12] arch: uapi: asm: mman.h: Let MADV_FREE have same value for all architectures Minchan Kim
2015-11-30 6:39 ` Minchan Kim [this message]
2015-11-30 6:39 ` [PATCH v5 05/12] mm: move lazily freed pages to inactive list Minchan Kim
2015-11-30 6:39 ` [PATCH v5 06/12] mm: mark stable page dirty in KSM Minchan Kim
2015-11-30 6:39 ` [PATCH v5 07/12] x86: add pmd_[dirty|mkclean] for THP Minchan Kim
2015-11-30 6:39 ` [PATCH v5 08/12] sparc: " Minchan Kim
2015-11-30 6:39 ` [PATCH v5 09/12] powerpc: " Minchan Kim
2015-11-30 6:39 ` [PATCH v5 10/12] arm: add pmd_mkclean " Minchan Kim
2015-11-30 6:39 ` [PATCH v5 11/12] arm64: " Minchan Kim
2015-11-30 6:39 ` [PATCH v5 12/12] mm: don't split THP page when syscall is called Minchan Kim
2016-01-28 7:16 ` [PATCH v5 00/12] MADV_FREE support Michael Kerrisk (man-pages)
2016-01-29 7:32 ` Minchan Kim
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