| Message ID | 1315210025-17727-1-git-send-email-avi@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 2011-09-05 10:07, Avi Kivity wrote: > To make good use of transparent hugepages, KVM requires that guest-physical > and host-virtual addresses share the low 21 bits (as opposed to just the low > 12 bits normally required). > > Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions > to avoid fragmentation. > > Signed-off-by: Avi Kivity <avi@redhat.com> > --- > oslib-posix.c | 14 +++++++++++++- > 1 files changed, 13 insertions(+), 1 deletions(-) > > diff --git a/oslib-posix.c b/oslib-posix.c > index 196099c..a304fb0 100644 > --- a/oslib-posix.c > +++ b/oslib-posix.c > @@ -35,6 +35,13 @@ > extern int daemon(int, int); > #endif > > +#if defined(__linux__) && defined(__x86_64__) > + /* Use 2MB alignment so transparent hugepages can be used by KVM */ Aren't transparent hugepages also available in TCG mode? Then just remove "by KVM" from subject and comment. Jan > +# define QEMU_VMALLOC_ALIGN (512 * 4096) > +#else > +# define QEMU_VMALLOC_ALIGN getpagesize() > +#endif > + > #include "config-host.h" > #include "sysemu.h" > #include "trace.h" > @@ -80,7 +87,12 @@ int qemu_daemon(int nochdir, int noclose) > void *qemu_vmalloc(size_t size) > { > void *ptr; > - ptr = qemu_memalign(getpagesize(), size); > + size_t align = QEMU_VMALLOC_ALIGN; > + > + if (size < align) { > + align = getpagesize(); > + } > + ptr = qemu_memalign(align, size); > trace_qemu_vmalloc(size, ptr); > return ptr; > }
On 09/05/2011 01:10 PM, Jan Kiszka wrote: > On 2011-09-05 10:07, Avi Kivity wrote: > > To make good use of transparent hugepages, KVM requires that guest-physical > > and host-virtual addresses share the low 21 bits (as opposed to just the low > > 12 bits normally required). > > > > Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions > > to avoid fragmentation. > > > > Signed-off-by: Avi Kivity<avi@redhat.com> > > --- > > oslib-posix.c | 14 +++++++++++++- > > 1 files changed, 13 insertions(+), 1 deletions(-) > > > > diff --git a/oslib-posix.c b/oslib-posix.c > > index 196099c..a304fb0 100644 > > --- a/oslib-posix.c > > +++ b/oslib-posix.c > > @@ -35,6 +35,13 @@ > > extern int daemon(int, int); > > #endif > > > > +#if defined(__linux__)&& defined(__x86_64__) > > + /* Use 2MB alignment so transparent hugepages can be used by KVM */ > > Aren't transparent hugepages also available in TCG mode? Then just > remove "by KVM" from subject and comment. They are, but they don't require the special alignment.
On 09/05/2011 03:07 AM, Avi Kivity wrote: > To make good use of transparent hugepages, KVM requires that guest-physical > and host-virtual addresses share the low 21 bits (as opposed to just the low > 12 bits normally required). > > Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions > to avoid fragmentation. > > Signed-off-by: Avi Kivity<avi@redhat.com> Applied. Thanks. Regards, Anthony Liguori > --- > oslib-posix.c | 14 +++++++++++++- > 1 files changed, 13 insertions(+), 1 deletions(-) > > diff --git a/oslib-posix.c b/oslib-posix.c > index 196099c..a304fb0 100644 > --- a/oslib-posix.c > +++ b/oslib-posix.c > @@ -35,6 +35,13 @@ > extern int daemon(int, int); > #endif > > +#if defined(__linux__)&& defined(__x86_64__) > + /* Use 2MB alignment so transparent hugepages can be used by KVM */ > +# define QEMU_VMALLOC_ALIGN (512 * 4096) > +#else > +# define QEMU_VMALLOC_ALIGN getpagesize() > +#endif > + > #include "config-host.h" > #include "sysemu.h" > #include "trace.h" > @@ -80,7 +87,12 @@ int qemu_daemon(int nochdir, int noclose) > void *qemu_vmalloc(size_t size) > { > void *ptr; > - ptr = qemu_memalign(getpagesize(), size); > + size_t align = QEMU_VMALLOC_ALIGN; > + > + if (size< align) { > + align = getpagesize(); > + } > + ptr = qemu_memalign(align, size); > trace_qemu_vmalloc(size, ptr); > return ptr; > }
diff --git a/oslib-posix.c b/oslib-posix.c index 196099c..a304fb0 100644 --- a/oslib-posix.c +++ b/oslib-posix.c @@ -35,6 +35,13 @@ extern int daemon(int, int); #endif +#if defined(__linux__) && defined(__x86_64__) + /* Use 2MB alignment so transparent hugepages can be used by KVM */ +# define QEMU_VMALLOC_ALIGN (512 * 4096) +#else +# define QEMU_VMALLOC_ALIGN getpagesize() +#endif + #include "config-host.h" #include "sysemu.h" #include "trace.h" @@ -80,7 +87,12 @@ int qemu_daemon(int nochdir, int noclose) void *qemu_vmalloc(size_t size) { void *ptr; - ptr = qemu_memalign(getpagesize(), size); + size_t align = QEMU_VMALLOC_ALIGN; + + if (size < align) { + align = getpagesize(); + } + ptr = qemu_memalign(align, size); trace_qemu_vmalloc(size, ptr); return ptr; }
To make good use of transparent hugepages, KVM requires that guest-physical and host-virtual addresses share the low 21 bits (as opposed to just the low 12 bits normally required). Adjust qemu_vmalloc() to honor that requirement. Ignore it for small regions to avoid fragmentation. Signed-off-by: Avi Kivity <avi@redhat.com> --- oslib-posix.c | 14 +++++++++++++- 1 files changed, 13 insertions(+), 1 deletions(-)