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Pat the watchdog less while producing a coredump. Prior to this change,

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we patted the watchdog approximately once per 4KB page of memory.  After
this change, we pat the watchdog approximately once per 128MB of memory.
On a sample machine, this translated to patting the watchdog approximately
every 5.4 seconds, which "seems reasonable". We can choose a different
value in the future, if warranted.

This has extensive field experience. It is a performance improvement, and
has not caused any known problems.

Reviewed by:	imp, kib
Sponsored by:	Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D14988
This commit is contained in:
jtl 2018-04-06 17:06:22 +00:00
parent 15af8ae175
commit 77cc11ce79
1 changed files with 12 additions and 4 deletions
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16
sys/amd64/amd64/minidump_machdep.c
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@ -62,7 +62,7 @@ static struct kerneldumpheader kdh;
/* Handle chunked writes. */
static size_t fragsz;
static void *dump_va;
static size_t counter, progress, dumpsize;
static size_t counter, progress, dumpsize, wdog_next;
CTASSERT(sizeof(*vm_page_dump) == 8);
static int dump_retry_count = 5;
@ -134,6 +134,9 @@ report_progress(size_t progress, size_t dumpsize)
}
}
/* Pat the watchdog approximately every 128MB of the dump. */
#define WDOG_DUMP_INTERVAL (128 * 1024 * 1024)
static int
blk_write(struct dumperinfo *di, char *ptr, vm_paddr_t pa, size_t sz)
{
@ -173,8 +176,13 @@ blk_write(struct dumperinfo *di, char *ptr, vm_paddr_t pa, size_t sz)
report_progress(progress, dumpsize);
counter &= (1<<24) - 1;
}
wdog_kern_pat(WD_LASTVAL);
if (progress <= wdog_next) {
wdog_kern_pat(WD_LASTVAL);
if (wdog_next > WDOG_DUMP_INTERVAL)
wdog_next -= WDOG_DUMP_INTERVAL;
else
wdog_next = 0;
}
if (ptr) {
error = dump_append(di, ptr, 0, len);
@ -313,7 +321,7 @@ minidumpsys(struct dumperinfo *di)
}
dumpsize += PAGE_SIZE;
progress = dumpsize;
wdog_next = progress = dumpsize;
/* Initialize mdhdr */
bzero(&mdhdr, sizeof(mdhdr));