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Default HZ value (1,000) on i386/amd64 is not very virtual machine friendly.

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Due to the nature of the beast it causes lot of unproductive overhead. This
is especially bad when running SMP kernel on VMWare with several virtual
processors - idle FreeBSD guest with SMP kernel takes 150% host CPU time on my
dual-core MacBook Pro when I am enabling two virtual CPUs, making even host
not very usable. Detect when we are running in the sandbox and reduce HZ
to 10 (can be adjusted via VM_HZ in the kernel config) in such cases. This
brings host CPU usage of idle FreeBSD/SMP on two virtual processors down
to 10%.

Detect most popular VM platforms out there - VMWare, Parallels, VirtualBox
and VirtualPC.

MFC after:	2 weeks
This commit is contained in:
sobomax 2008-10-27 06:25:02 +00:00
parent 322737440f
commit 6b076dc603
1 changed files with 39 additions and 1 deletions
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40
sys/kern/subr_param.c
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@ -57,6 +57,13 @@ __FBSDID("$FreeBSD$");
# else
# define HZ 100
# endif
# ifndef HZ_VM
# define HZ_VM 10
# endif
#else
# ifndef HZ_VM
# define HZ_VM HZ
# endif
#endif
#define NPROC (20 + 16 * maxusers)
#ifndef NBUF
@ -111,6 +118,30 @@ SYSCTL_ULONG(_kern, OID_AUTO, sgrowsiz, CTLFLAG_RDTUN, &sgrowsiz, 0,
*/
struct buf *swbuf;
char *vm_pnames[] = {
"VMware Virtual Platform", /* VMWare VM */
"Virtual Machine", /* Microsoft VirtualPC */
"VirtualBox", /* Sun xVM VirtualBox */
"Parallels Virtual Platform", /* Parallels VM */
NULL
};
static int
detect_virtual(void)
{
char *sysenv;
int i;
sysenv = getenv("smbios.system.product");
if (sysenv != NULL) {
for (i = 0; vm_pnames[i] != NULL; i++) {
if (strcmp(sysenv, vm_pnames[i]) == 0)
return 1;
}
}
return 0;
}
/*
* Boot time overrides that are not scaled against main memory
*/
@ -118,8 +149,15 @@ void
init_param1(void)
{
hz = HZ;
hz = -1;
TUNABLE_INT_FETCH("kern.hz", &hz);
if (hz == -1) {
if (detect_virtual()) {
hz = HZ_VM;
} else {
hz = HZ;
}
}
tick = 1000000 / hz;
#ifdef VM_SWZONE_SIZE_MAX