The PFN_EXCLUDED value is used to control at which point a run of
zeros in the bitmap (zeros denote excluded pages) is large enough
to warrant truncating the current output segment and to create a
new output segment (containing non-excluded pages), in an ELF dump.
If the run is smaller than PFN_EXCLUDED, then those excluded pages
are still output in the ELF dump, for the current output segment.
By using smaller values of PFN_EXCLUDED, the resulting dump file
size can be made smaller by actually removing more excluded pages
from the resulting dump file.
This patch adds the command line option --exclude-threshold=<value>
to indicate the threshold. The default is 256, the legacy value
of PFN_EXCLUDED. The smallest value permitted is 1.
Using an existing vmcore, this was tested by the following:
% makedumpfile -E -d31 --exclude-threshold=256 -x vmlinux vmcore newvmcore256
% makedumpfile -E -d31 --exclude-threshold=4 -x vmlinux vmcore newvmcore4
I utilize -d31 in order to exclude as many page types as possible,
resulting in a [significantly] smaller file sizes than the original
vmcore.
-rwxrwx--- 1 edevolde edevolde 4034564096 Jun 27 10:24 vmcore
-rw------- 1 edevolde edevolde 119808156 Jul 6 13:01 newvmcore256
-rw------- 1 edevolde edevolde 100811276 Jul 6 13:08 newvmcore4
The use of smaller value of PFN_EXCLUDED increases the number of
output segments (the 'Number of program headers' in the readelf
output) in the ELF dump file.
% readelf -h vmcore
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: CORE (Core file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 64 (bytes into file)
Start of section headers: 0 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 6
^^^
Size of section headers: 0 (bytes)
Number of section headers: 0
Section header string table index: 0
% readelf -h newvmcore256
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: CORE (Core file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 64 (bytes into file)
Start of section headers: 0 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 18
^^^
Size of section headers: 0 (bytes)
Number of section headers: 0
Section header string table index: 0
% readelf -h newvmcore4
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: CORE (Core file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 64 (bytes into file)
Start of section headers: 0 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 244
^^^
Size of section headers: 0 (bytes)
Number of section headers: 0
Section header string table index: 0
The newvmcore4 has an even smaller file size than newvmcore256, with
the small price being that there are now 244 rather than 18 segments
in the dump file.
And with a larger number of segments, loading both vmcore and newvmcore4
into 'crash' resulted in identical outputs when run with the dmesg, ps,
files, mount, and net sub-commands.
Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
---
v1: Posted 06jul2017 to kexec-tools mailing list
- original
---
makedumpfile.c | 20 +++++++++++++++++---
makedumpfile.h | 4 +++-
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/makedumpfile.c b/makedumpfile.c
index e69b6df..940f64c 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -7236,7 +7236,7 @@ get_loads_dumpfile_cyclic(void)
/*
* If the number of the contiguous pages to be excluded
- * is 256 or more, those pages are excluded really.
+ * is PFN_EXCLUDED or more, those pages are excluded really.
* And a new PT_LOAD segment is created.
*/
if (num_excluded >= PFN_EXCLUDED) {
@@ -7352,7 +7352,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
continue;
/*
* If the number of the contiguous pages to be excluded
- * is 255 or less, those pages are not excluded.
+ * is less than PFN_EXCLUDED, those pages are not excluded.
*/
} else if (num_excluded < PFN_EXCLUDED) {
if ((pfn == pfn_end - 1) && frac_tail) {
@@ -7370,7 +7370,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
/*
* If the number of the contiguous pages to be excluded
- * is 256 or more, those pages are excluded really.
+ * is PFN_EXCLUDED or more, those pages are excluded really.
* And a new PT_LOAD segment is created.
*/
load.p_memsz = memsz;
@@ -11007,6 +11007,7 @@ static struct option longopts[] = {
{"splitblock-size", required_argument, NULL, OPT_SPLITBLOCK_SIZE},
{"work-dir", required_argument, NULL, OPT_WORKING_DIR},
{"num-threads", required_argument, NULL, OPT_NUM_THREADS},
+ {"exclude-threshold", required_argument, NULL, OPT_PFN_EXCLUDE_THRESHOLD},
{0, 0, 0, 0}
};
@@ -11044,6 +11045,14 @@ main(int argc, char *argv[])
*/
info->flag_usemmap = MMAP_TRY;
+ /*
+ * A run of zeros in the bitmap (excluded pages) of less than
+ * pfn_excluded_threshold in length will still be dumped. Runs greater
+ * than or equal to pfn_excluded_threshold will result in the creation
+ * of a new output segment, for ELF dumps.
+ */
+ info->pfn_exclude_threshold = 256;
+
info->block_order = DEFAULT_ORDER;
message_level = DEFAULT_MSG_LEVEL;
while ((opt = getopt_long(argc, argv, "b:cDd:eEFfg:hi:lpRvXx:", longopts,
@@ -11163,6 +11172,11 @@ main(int argc, char *argv[])
case OPT_NUM_THREADS:
info->num_threads = MAX(atoi(optarg), 0);
break;
+ case OPT_PFN_EXCLUDE_THRESHOLD:
+ info->pfn_exclude_threshold = strtoul(optarg, NULL, 0);
+ if (0 == info->pfn_exclude_threshold)
+ info->pfn_exclude_threshold = 1;
+ break;
case '?':
MSG("Commandline parameter is invalid.\n");
MSG("Try `makedumpfile --help' for more information.\n");
diff --git a/makedumpfile.h b/makedumpfile.h
index e32e567..33d3eb0 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -216,7 +216,7 @@ isAnon(unsigned long mapping)
#define BITPERBYTE (8)
#define PGMM_CACHED (512)
-#define PFN_EXCLUDED (256)
+#define PFN_EXCLUDED (info->pfn_exclude_threshold)
#define BUFSIZE (1024)
#define BUFSIZE_FGETS (1500)
#define BUFSIZE_BITMAP (4096)
@@ -1139,6 +1139,7 @@ struct DumpInfo {
long page_size; /* size of page */
long page_shift;
mdf_pfn_t max_mapnr; /* number of page descriptor */
+ unsigned long pfn_exclude_threshold;
unsigned long page_offset;
unsigned long section_size_bits;
unsigned long max_physmem_bits;
@@ -2143,6 +2144,7 @@ struct elf_prstatus {
#define OPT_SPLITBLOCK_SIZE OPT_START+14
#define OPT_WORKING_DIR OPT_START+15
#define OPT_NUM_THREADS OPT_START+16
+#define OPT_PFN_EXCLUDE_THRESHOLD OPT_START+17
/*
* Function Prototype.
--
2.7.4
