[Crash-utility] [PATCH v2] diskdump: Optimize the boot time
1.) The vmcore file maybe very big.
For example, I have a vmcore file which is over 23G,
and the panic kernel had 767.6G memory,
its max_sect_len is 4468736.
Current code costs too much time to do the following loop:
..............................................
for (i = 1; i < max_sect_len + 1; i++) {
dd->valid_pages[i] = dd->valid_pages[i - 1];
for (j = 0; j < BITMAP_SECT_LEN; j++, pfn++)
if (page_is_dumpable(pfn))
dd->valid_pages[i]++;
..............................................
For my case, it costs about 56 seconds to finish the
big loop.
This patch moves the hweightXX macros to defs.h,
and uses hweight64 to optimize the loop.
For my vmcore, the loop only costs about one second now.
2.) Tests result:
# cat ./commands.txt
quit
Before:
#echo 3 > /proc/sys/vm/drop_caches;
#time ./crash -i ./commands.txt /root/t/vmlinux /root/t/vmcore > /dev/null
2>&1
............................
real 1m54.259s
user 1m12.494s
sys 0m3.857s
............................
After this patch:
#echo 3 > /proc/sys/vm/drop_caches;
#time ./crash -i ./commands.txt /root/t/vmlinux /root/t/vmcore > /dev/null
2>&1
............................
real 0m55.217s
user 0m15.114s
sys 0m3.560s
............................
Signed-off-by: Huang Shijie <shijie(a)os.amperecomputing.com>
---
v1 --> v2:
1.) change u64 to ulonglong.
2.) compile this patch in x86_64.
---
defs.h | 20 ++++++++++++++++++++
diskdump.c | 12 +++++++++---
sbitmap.c | 19 -------------------
3 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/defs.h b/defs.h
index 81ac049..1e8360d 100644
--- a/defs.h
+++ b/defs.h
@@ -4531,6 +4531,26 @@ struct machine_specific {
#define NUM_IN_BITMAP(bitmap, x) (bitmap[(x)/BITS_PER_LONG] & NUM_TO_BIT(x))
#define SET_BIT(bitmap, x) (bitmap[(x)/BITS_PER_LONG] |= NUM_TO_BIT(x))
+static inline unsigned int __const_hweight8(unsigned long w)
+{
+ return
+ (!!((w) & (1ULL << 0))) +
+ (!!((w) & (1ULL << 1))) +
+ (!!((w) & (1ULL << 2))) +
+ (!!((w) & (1ULL << 3))) +
+ (!!((w) & (1ULL << 4))) +
+ (!!((w) & (1ULL << 5))) +
+ (!!((w) & (1ULL << 6))) +
+ (!!((w) & (1ULL << 7)));
+}
+
+#define __const_hweight16(w) (__const_hweight8(w) + __const_hweight8((w) >> 8))
+#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
+#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
+
+#define hweight32(w) __const_hweight32(w)
+#define hweight64(w) __const_hweight64(w)
+
/*
* precision lengths for fprintf
*/
diff --git a/diskdump.c b/diskdump.c
index d567427..ff1e9a3 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -547,6 +547,7 @@ read_dump_header(char *file)
ulong pfn;
int i, j, max_sect_len;
int is_split = 0;
+ ulonglong tmp, *bitmap;
if (block_size < 0)
return FALSE;
@@ -899,11 +900,16 @@ restart:
dd->valid_pages = calloc(sizeof(ulong), max_sect_len + 1);
dd->max_sect_len = max_sect_len;
+
+ /* It is safe to convert it to (ulonglong *). */
+ bitmap = (ulonglong *)dd->dumpable_bitmap;
for (i = 1; i < max_sect_len + 1; i++) {
dd->valid_pages[i] = dd->valid_pages[i - 1];
- for (j = 0; j < BITMAP_SECT_LEN; j++, pfn++)
- if (page_is_dumpable(pfn))
- dd->valid_pages[i]++;
+ for (j = 0; j < BITMAP_SECT_LEN; j += 64, pfn += 64) {
+ tmp = bitmap[pfn >> 6];
+ if (tmp)
+ dd->valid_pages[i] += hweight64(tmp);
+ }
}
return TRUE;
diff --git a/sbitmap.c b/sbitmap.c
index 286259f..96a61e6 100644
--- a/sbitmap.c
+++ b/sbitmap.c
@@ -49,25 +49,6 @@ struct sbitmapq_data {
static uint sb_flags = 0;
-static inline unsigned int __const_hweight8(unsigned long w)
-{
- return
- (!!((w) & (1ULL << 0))) +
- (!!((w) & (1ULL << 1))) +
- (!!((w) & (1ULL << 2))) +
- (!!((w) & (1ULL << 3))) +
- (!!((w) & (1ULL << 4))) +
- (!!((w) & (1ULL << 5))) +
- (!!((w) & (1ULL << 6))) +
- (!!((w) & (1ULL << 7)));
-}
-
-#define __const_hweight16(w) (__const_hweight8(w) + __const_hweight8((w) >> 8))
-#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
-#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
-
-#define hweight32(w) __const_hweight32(w)
-#define hweight64(w) __const_hweight64(w)
#define BIT(nr) (1UL << (nr))
--
2.30.2