Author: gavin
Date: Sat Dec 31 13:24:53 2011
New Revision: 229085
URL: http://svn.freebsd.org/changeset/base/229085
Log:
Default to not performing the early-boot memory tests when we detect we
are booting inside a VM. There are three reasons to disable this:
o It causes the VM host to believe that all the tested pages or RAM are
in use. This in turn may force the host to page out pages of RAM
belonging to other VMs, or otherwise cause problems with fair resource
sharing on the VM cluster.
o It adds significant time to the boot process (around 1 second/Gig in
testing)
o It is unnecessary - the host should have already verified that the
memory is functional etc.
Note that this simply changes the default when in a VM - it can still be
overridden using the hw.memtest.tests tunable.
MFC after: 4 weeks
Modified:
head/sys/amd64/amd64/machdep.c
head/sys/i386/i386/machdep.c
Modified: head/sys/amd64/amd64/machdep.c
==============================================================================
--- head/sys/amd64/amd64/machdep.c Sat Dec 31 13:23:04 2011
(r229084)
+++ head/sys/amd64/amd64/machdep.c Sat Dec 31 13:24:53 2011
(r229085)
@@ -1401,10 +1401,13 @@ getmemsize(caddr_t kmdp, u_int64_t first
Maxmem = atop(physmem_tunable);
/*
- * By default keep the memtest enabled. Use a general name so that
+ * By default enable the memory test on real hardware, and disable
+ * it if we appear to be running in a VM. This avoids touching all
+ * pages unnecessarily, which doesn't matter on real hardware but is
+ * bad for shared VM hosts. Use a general name so that
* one could eventually do more with the code than just disable it.
*/
- memtest = 1;
+ memtest = (vm_guest > VM_GUEST_NO) ? 0 : 1;
TUNABLE_ULONG_FETCH("hw.memtest.tests", &memtest);
/*
Modified: head/sys/i386/i386/machdep.c
==============================================================================
--- head/sys/i386/i386/machdep.c Sat Dec 31 13:23:04 2011
(r229084)
+++ head/sys/i386/i386/machdep.c Sat Dec 31 13:24:53 2011
(r229085)
@@ -2369,10 +2369,13 @@ physmap_done:
Maxmem = atop(physmap[physmap_idx + 1]);
/*
- * By default keep the memtest enabled. Use a general name so that
+ * By default enable the memory test on real hardware, and disable
+ * it if we appear to be running in a VM. This avoids touching all
+ * pages unnecessarily, which doesn't matter on real hardware but is
+ * bad for shared VM hosts. Use a general name so that
* one could eventually do more with the code than just disable it.
*/
- memtest = 1;
+ memtest = (vm_guest > VM_GUEST_NO) ? 0 : 1;
TUNABLE_ULONG_FETCH("hw.memtest.tests", &memtest);
if (atop(physmap[physmap_idx + 1]) != Maxmem &&
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