Re: [PATCH 0/3] makedumpfile: hugepage filtering for vmcore dump

Atsushi Kumagai
2013-11-06T02:25:59Z

(2013/11/06 5:27), Vivek Goyal wrote:
> On Tue, Nov 05, 2013 at 09:45:32PM +0800, Jingbai Ma wrote:
>> This patch set intend to exclude unnecessary hugepages from vmcore dump file.
>>
>> This patch requires the kernel patch to export necessary data structures into
>> vmcore: "kexec: export hugepage data structure into vmcoreinfo"
>> http://lists.infradead.org/pipermail/kexec/2013-November/009997.html
>>
>> This patch introduce two new dump levels 32 and 64 to exclude all unused and
>> active hugepages. The level to exclude all unnecessary pages will be 127 now.
>
> Interesting. Why hugepages should be treated any differentely than normal
> pages?
>
> If user asked to filter out free page, then it should be filtered and
> it should not matter whether it is a huge page or not?

I'm making a RFC patch of hugepages filtering based on such policy.

I attach the prototype version.
It's able to filter out also THPs, and suitable for cyclic processing
because it depends on mem_map and looking up it can be divided into
cycles. This is the same idea as page_is_buddy().

So I think it's better.

--
Thanks
Atsushi Kumagai

From: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Date: Wed, 6 Nov 2013 10:10:43 +0900
Subject: [PATCH] [RFC] Exclude hugepages.

Signed-off-by: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
---
makedumpfile.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
makedumpfile.h | 8 ++++
2 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index 428c53e..75b7123 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -63,6 +63,7 @@ do { \

static void check_cyclic_buffer_overrun(void);
static void setup_page_is_buddy(void);
+static void setup_page_is_hugepage(void);

void
initialize_tables(void)
@@ -270,6 +271,18 @@ update_mmap_range(off_t offset, int initial) {
}

static int
+page_is_hugepage(unsigned long flags) {
+ if (NUMBER(PG_head) != NOT_FOUND_NUMBER) {
+ return isHead(flags);
+ } else if (NUMBER(PG_tail) != NOT_FOUND_NUMBER) {
+ return isTail(flags);
+ }if (NUMBER(PG_compound) != NOT_FOUND_NUMBER) {
+ return isCompound(flags);
+ }
+ return 0;
+}
+
+static int
is_mapped_with_mmap(off_t offset) {

if (info->flag_usemmap
@@ -1107,6 +1120,8 @@ get_symbol_info(void)
SYMBOL_ARRAY_LENGTH_INIT(node_remap_start_pfn,
"node_remap_start_pfn");

+ SYMBOL_INIT(free_huge_page, "free_huge_page");
+
return TRUE;
}

@@ -1214,11 +1229,19 @@ get_structure_info(void)

ENUM_NUMBER_INIT(PG_lru, "PG_lru");
ENUM_NUMBER_INIT(PG_private, "PG_private");
+ ENUM_NUMBER_INIT(PG_head, "PG_head");
+ ENUM_NUMBER_INIT(PG_tail, "PG_tail");
+ ENUM_NUMBER_INIT(PG_compound, "PG_compound");
ENUM_NUMBER_INIT(PG_swapcache, "PG_swapcache");
ENUM_NUMBER_INIT(PG_buddy, "PG_buddy");
ENUM_NUMBER_INIT(PG_slab, "PG_slab");
ENUM_NUMBER_INIT(PG_hwpoison, "PG_hwpoison");

+ if (NUMBER(PG_head) == NOT_FOUND_NUMBER &&
+ NUMBER(PG_compound) == NOT_FOUND_NUMBER)
+ /* Pre-2.6.26 kernels did not have pageflags */
+ NUMBER(PG_compound) = PG_compound_ORIGINAL;
+
ENUM_TYPE_SIZE_INIT(pageflags, "pageflags");

TYPEDEF_SIZE_INIT(nodemask_t, "nodemask_t");
@@ -1603,6 +1626,7 @@ write_vmcoreinfo_data(void)
WRITE_SYMBOL("node_remap_start_vaddr", node_remap_start_vaddr);
WRITE_SYMBOL("node_remap_end_vaddr", node_remap_end_vaddr);
WRITE_SYMBOL("node_remap_start_pfn", node_remap_start_pfn);
+ WRITE_SYMBOL("free_huge_page", free_huge_page);

/*
* write the structure size of 1st kernel
@@ -1685,6 +1709,9 @@ write_vmcoreinfo_data(void)

WRITE_NUMBER("PG_lru", PG_lru);
WRITE_NUMBER("PG_private", PG_private);
+ WRITE_NUMBER("PG_head", PG_head);
+ WRITE_NUMBER("PG_tail", PG_tail);
+ WRITE_NUMBER("PG_compound", PG_compound);
WRITE_NUMBER("PG_swapcache", PG_swapcache);
WRITE_NUMBER("PG_buddy", PG_buddy);
WRITE_NUMBER("PG_slab", PG_slab);
@@ -1932,6 +1959,7 @@ read_vmcoreinfo(void)
READ_SYMBOL("node_remap_start_vaddr", node_remap_start_vaddr);
READ_SYMBOL("node_remap_end_vaddr", node_remap_end_vaddr);
READ_SYMBOL("node_remap_start_pfn", node_remap_start_pfn);
+ READ_SYMBOL("free_huge_page", free_huge_page);

READ_STRUCTURE_SIZE("page", page);
READ_STRUCTURE_SIZE("mem_section", mem_section);
@@ -2000,6 +2028,9 @@ read_vmcoreinfo(void)

READ_NUMBER("PG_lru", PG_lru);
READ_NUMBER("PG_private", PG_private);
+ READ_NUMBER("PG_head", PG_head);
+ READ_NUMBER("PG_tail", PG_tail);
+ READ_NUMBER("PG_compound", PG_compound);
READ_NUMBER("PG_swapcache", PG_swapcache);
READ_NUMBER("PG_slab", PG_slab);
READ_NUMBER("PG_buddy", PG_buddy);
@@ -3126,6 +3157,9 @@ out:
if (!get_value_for_old_linux())
return FALSE;

+ /* Get page flags for compound pages */
+ setup_page_is_hugepage();
+
/* use buddy identification of free pages whether cyclic or not */
/* (this can reduce pages scan of 1TB memory from 60sec to 30sec) */
if (info->dump_level & DL_EXCLUDE_FREE)
@@ -4197,6 +4231,23 @@ out:
"follow free lists instead of mem_map array.\n");
}

+static void
+setup_page_is_hugepage(void)
+{
+ if (NUMBER(PG_head) != NOT_FOUND_NUMBER) {
+ if (NUMBER(PG_tail) == NOT_FOUND_NUMBER) {
+ /* If PG_tail is not explicitly saved, then assume
+ * that it immediately follows PG_head.
+ */
+ NUMBER(PG_tail) = NUMBER(PG_head) + 1;
+ }
+ } else if ((NUMBER(PG_compound) != NOT_FOUND_NUMBER)
+ && (info->dump_level & DL_EXCLUDE_USER_DATA)) {
+ MSG("Compound page bit could not be determined: ");
+ MSG("huge pages will NOT be filtered.\n");
+ }
+}
+
/*
* If using a dumpfile in kdump-compressed format as a source file
* instead of /proc/vmcore, 1st-bitmap of a new dumpfile must be
@@ -4404,8 +4455,9 @@ __exclude_unnecessary_pages(unsigned long mem_map,
unsigned long long pfn_read_start, pfn_read_end, index_pg;
unsigned char page_cache[SIZE(page) * PGMM_CACHED];
unsigned char *pcache;
- unsigned int _count, _mapcount = 0;
+ unsigned int _count, _mapcount = 0, compound_order = 0;
unsigned long flags, mapping, private = 0;
+ unsigned long hugetlb_dtor;

/*
* Refresh the buffer of struct page, when changing mem_map.
@@ -4459,6 +4511,27 @@ __exclude_unnecessary_pages(unsigned long mem_map,
flags = ULONG(pcache + OFFSET(page.flags));
_count = UINT(pcache + OFFSET(page._count));
mapping = ULONG(pcache + OFFSET(page.mapping));
+
+ if (index_pg < PGMM_CACHED - 1) {
+ compound_order = ULONG(pcache + SIZE(page) + OFFSET(page.lru)
+ + OFFSET(list_head.prev));
+ hugetlb_dtor = ULONG(pcache + SIZE(page) + OFFSET(page.lru)
+ + OFFSET(list_head.next));
+ } else if (pfn + 1 < pfn_end) {
+ unsigned char page_cache_next[SIZE(page)];
+ if (!readmem(VADDR, mem_map, page_cache_next, SIZE(page))) {
+ ERRMSG("Can't read the buffer of struct page.\n");
+ return FALSE;
+ }
+ compound_order = ULONG(page_cache_next + OFFSET(page.lru)
+ + OFFSET(list_head.prev));
+ hugetlb_dtor = ULONG(page_cache_next + OFFSET(page.lru)
+ + OFFSET(list_head.next));
+ } else {
+ compound_order = 0;
+ hugetlb_dtor = 0;
+ }
+
if (OFFSET(page._mapcount) != NOT_FOUND_STRUCTURE)
_mapcount = UINT(pcache + OFFSET(page._mapcount));
if (OFFSET(page.private) != NOT_FOUND_STRUCTURE)
@@ -4497,6 +4570,10 @@ __exclude_unnecessary_pages(unsigned long mem_map,
&& !isPrivate(flags) && !isAnon(mapping)) {
if (clear_bit_on_2nd_bitmap_for_kernel(pfn))
pfn_cache++;
+ /*
+ * NOTE: If THP for cache is introduced, the check for
+ * compound pages is needed here.
+ */
}
/*
* Exclude the cache page with the private page.
@@ -4506,14 +4583,49 @@ __exclude_unnecessary_pages(unsigned long mem_map,
&& !isAnon(mapping)) {
if (clear_bit_on_2nd_bitmap_for_kernel(pfn))
pfn_cache_private++;
+ /*
+ * NOTE: If THP for cache is introduced, the check for
+ * compound pages is needed here.
+ */
}
/*
* Exclude the data page of the user process.
*/
- else if ((info->dump_level & DL_EXCLUDE_USER_DATA)
- && isAnon(mapping)) {
- if (clear_bit_on_2nd_bitmap_for_kernel(pfn))
- pfn_user++;
+ else if (info->dump_level & DL_EXCLUDE_USER_DATA) {
+ /*
+ * Exclude the anonnymous pages as user pages.
+ */
+ if (isAnon(mapping)) {
+ if (clear_bit_on_2nd_bitmap_for_kernel(pfn))
+ pfn_user++;
+
+ /*
+ * Check the compound page
+ */
+ if (page_is_hugepage(flags) && compound_order > 0) {
+ int i, nr_pages = 1 << compound_order;
+
+ for (i = 1; i < nr_pages; ++i) {
+ if (clear_bit_on_2nd_bitmap_for_kernel(pfn + i))
+ pfn_user++;
+ }
+ pfn += nr_pages - 2;
+ mem_map += (nr_pages - 1) * SIZE(page);
+ }
+ }
+ /*
+ * Exclude the hugetlbfs pages as user pages.
+ */
+ else if (hugetlb_dtor == SYMBOL(free_huge_page)) {
+ int i, nr_pages = 1 << compound_order;
+
+ for (i = 0; i < nr_pages; ++i) {
+ if (clear_bit_on_2nd_bitmap_for_kernel(pfn + i))
+ pfn_user++;
+ }
+ pfn += nr_pages - 1;
+ mem_map += (nr_pages - 1) * SIZE(page);
+ }
}
/*
* Exclude the hwpoison page.
diff --git a/makedumpfile.h b/makedumpfile.h
index 3a7e61a..d6ee832 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -74,6 +74,7 @@ int get_mem_type(void);
#define PG_lru_ORIGINAL (5)
#define PG_slab_ORIGINAL (7)
#define PG_private_ORIGINAL (11) /* Has something at ->private */
+#define PG_compound_ORIGINAL (14) /* Is part of a compound page */
#define PG_swapcache_ORIGINAL (15) /* Swap page: swp_entry_t in private */

#define PAGE_BUDDY_MAPCOUNT_VALUE_v2_6_38 (-2)
@@ -140,6 +141,9 @@ test_bit(int nr, unsigned long addr)

#define isLRU(flags) test_bit(NUMBER(PG_lru), flags)
#define isPrivate(flags) test_bit(NUMBER(PG_private), flags)
+#define isHead(flags) test_bit(NUMBER(PG_head), flags)
+#define isTail(flags) test_bit(NUMBER(PG_tail), flags)
+#define isCompound(flags) test_bit(NUMBER(PG_compound), flags)
#define isSwapCache(flags) test_bit(NUMBER(PG_swapcache), flags)
#define isHWPOISON(flags) (test_bit(NUMBER(PG_hwpoison), flags) \
&& (NUMBER(PG_hwpoison) != NOT_FOUND_NUMBER))
@@ -1124,6 +1128,7 @@ struct symbol_table {
unsigned long long node_remap_start_vaddr;
unsigned long long node_remap_end_vaddr;
unsigned long long node_remap_start_pfn;
+ unsigned long long free_huge_page;

/*
* for Xen extraction
@@ -1383,6 +1388,9 @@ struct number_table {
*/
long PG_lru;
long PG_private;
+ long PG_head;
+ long PG_tail;
+ long PG_compound;
long PG_swapcache;
long PG_buddy;
long PG_slab;
--
1.8.0.2