On Mon, Sep 14, 2015 at 10:31:45PM +0300, Ebru Akagunduz wrote:
> This patch makes swapin readahead to improve thp collapse rate.
> When khugepaged scanned pages, there can be a few of the pages
> in swap area.
>
> With the patch THP can collapse 4kB pages into a THP when
> there are up to max_ptes_swap swap ptes in a 2MB range.
>
> The patch was tested with a test program that allocates
> 400B of memory, writes to it, and then sleeps. I force
> the system to swap out all. Afterwards, the test program
> touches the area by writing, it skips a page in each
> 20 pages of the area.
>
> Without the patch, system did not swap in readahead.
> THP rate was %65 of the program of the memory, it
> did not change over time.
>
> With this patch, after 10 minutes of waiting khugepaged had
> collapsed %99 of the program's memory.
>
> Signed-off-by: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
[ resend with correct TO/CC lists]
>From 9b28cf3159ff200d4a2543d73a06ae84d050aea2 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Thu, 17 Sep 2015 16:35:57 +0300
Subject: [PATCH] khugepaged: avoid usage of uninitialized variable 'isolated'
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In file included from include/trace/events/huge_memory.h:7:0,
from mm/huge_memory.c:62:
include/linux/tracepoint.h:141:5: warning: ‘isolated’ may be used uninitialized in this function [-Wmaybe-uninitialized]
((void(*)(proto))(it_func))(args); \
^
mm/huge_memory.c:2327:6: note: ‘isolated’ was declared here
int isolated, result = 0;
We make use of isolated in error path before it get initialized.
The patch also makes trivial cleanup of exit path of the function.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5ad5c443cc94..857f92e85c38 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2656,8 +2656,6 @@ static void __collapse_huge_page_swapin(struct mm_struct *mm,
trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
}
-
-
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
@@ -2669,7 +2667,7 @@ static void collapse_huge_page(struct mm_struct *mm,
pgtable_t pgtable;
struct page *new_page;
spinlock_t *pmd_ptl, *pte_ptl;
- int isolated, result = 0;
+ int isolated = 0, result = 0;
unsigned long hstart, hend;
struct mem_cgroup *memcg;
unsigned long mmun_start; /* For mmu_notifiers */
@@ -2805,9 +2803,6 @@ static void collapse_huge_page(struct mm_struct *mm,
result = SCAN_SUCCEED;
out_up_write:
up_write(&mm->mmap_sem);
- trace_mm_collapse_huge_page(mm, isolated, result);
- return;
-
out_nolock:
trace_mm_collapse_huge_page(mm, isolated, result);
return;
--
Kirill A. Shutemov
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