Add a new kernel option, MALLOC_MAKE_FAILURES, which compiles
in a debugging feature causing M_NOWAIT allocations to fail at a specified rate. This can be useful for detecting poor handling of M_NOWAIT: the most frequent problems I've bumped into are unconditional deference of the pointer even though it's NULL, and hangs as a result of a lost event where memory for the event couldn't be allocated. Two sysctls are added: debug.malloc.failure_rate How often to generate a failure: if set to 0 (default), this feature is disabled. Otherwise, the frequency of failures -- I've been using 10 (one in ten mallocs fails), but other popular settings might be much lower or much higher. debug.malloc.failure_count Number of times a coerced malloc failure has occurred as a result of this feature. Useful for tracking what might have happened and whether failures are being generated. Useful possible additions: tying failure rate to malloc type, printfs indicating the thread that experienced the coerced failure. Reviewed by: jeffr, jhb
This commit is contained in:
parent
90836fcf7d
commit
eae870cdb4
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=112689
@ -473,6 +473,7 @@ VM_KMEM_SIZE opt_vm.h
|
||||
VM_KMEM_SIZE_SCALE opt_vm.h
|
||||
VM_KMEM_SIZE_MAX opt_vm.h
|
||||
NO_SWAPPING opt_vm.h
|
||||
MALLOC_MAKE_FAILURES opt_vm.h
|
||||
MALLOC_PROFILE opt_vm.h
|
||||
PQ_NOOPT opt_vmpage.h
|
||||
PQ_NORMALCACHE opt_vmpage.h
|
||||
|
@ -138,6 +138,23 @@ static int sysctl_kern_malloc(SYSCTL_HANDLER_ARGS);
|
||||
/* time_uptime of last malloc(9) failure */
|
||||
static time_t t_malloc_fail;
|
||||
|
||||
#ifdef MALLOC_MAKE_FAILURES
|
||||
/*
|
||||
* Causes malloc failures every (n) mallocs with M_NOWAIT. If set to 0,
|
||||
* doesn't cause failures.
|
||||
*/
|
||||
SYSCTL_NODE(_debug, OID_AUTO, malloc, CTLFLAG_RD, 0,
|
||||
"Kernel malloc debugging options");
|
||||
|
||||
static int malloc_failure_rate;
|
||||
static int malloc_nowait_count;
|
||||
static int malloc_failure_count;
|
||||
SYSCTL_INT(_debug_malloc, OID_AUTO, failure_rate, CTLFLAG_RW,
|
||||
&malloc_failure_rate, 0, "Every (n) mallocs with M_NOWAIT will fail");
|
||||
SYSCTL_INT(_debug_malloc, OID_AUTO, failure_count, CTLFLAG_RD,
|
||||
&malloc_failure_count, 0, "Number of imposed M_NOWAIT malloc failures");
|
||||
#endif
|
||||
|
||||
int
|
||||
malloc_last_fail(void)
|
||||
{
|
||||
@ -187,6 +204,15 @@ malloc(size, type, flags)
|
||||
#if 0
|
||||
if (size == 0)
|
||||
Debugger("zero size malloc");
|
||||
#endif
|
||||
#ifdef MALLOC_MAKE_FAILURES
|
||||
if ((flags & M_NOWAIT) && (malloc_failure_rate != 0)) {
|
||||
atomic_add_int(&malloc_nowait_count, 1);
|
||||
if ((malloc_nowait_count % malloc_failure_rate) == 0) {
|
||||
atomic_add_int(&malloc_failure_count, 1);
|
||||
return (NULL);
|
||||
}
|
||||
}
|
||||
#endif
|
||||
if (flags & M_WAITOK)
|
||||
KASSERT(curthread->td_intr_nesting_level == 0,
|
||||
|
Loading…
Reference in New Issue
Block a user