* [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations @ 2012-10-05 19:47 Luiz Capitulino 2012-10-15 18:57 ` Luiz Capitulino 0 siblings, 1 reply; 5+ messages in thread From: Luiz Capitulino @ 2012-10-05 19:47 UTC (permalink / raw) To: qemu-devel; +Cc: aarcange, jan.kiszka This makes it possible for QEMU to use transparent huge pages (THP) when transparent_hugepage/enabled=madvise. Otherwise THP is only used when it's enabled system wide. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> --- exec.c | 1 + osdep.h | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/exec.c b/exec.c index 1114a09..7504909 100644 --- a/exec.c +++ b/exec.c @@ -2584,6 +2584,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); qemu_ram_setup_dump(new_block->host, size); + qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE); if (kvm_enabled()) kvm_setup_guest_memory(new_block->host, size); diff --git a/osdep.h b/osdep.h index cb213e0..c5fd3d9 100644 --- a/osdep.h +++ b/osdep.h @@ -108,6 +108,11 @@ void qemu_vfree(void *ptr); #else #define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID #endif +#ifdef MADV_HUGEPAGE +#define QEMU_MADV_HUGEPAGE MADV_HUGEPAGE +#else +#define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID +#endif #elif defined(CONFIG_POSIX_MADVISE) -- 1.7.12.315.g682ce8b ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations 2012-10-05 19:47 [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations Luiz Capitulino @ 2012-10-15 18:57 ` Luiz Capitulino 2012-10-15 21:14 ` Michael Tokarev 2012-10-21 3:46 ` Aurelien Jarno 0 siblings, 2 replies; 5+ messages in thread From: Luiz Capitulino @ 2012-10-15 18:57 UTC (permalink / raw) To: aliguori; +Cc: aarcange, jan.kiszka, qemu-devel On Fri, 5 Oct 2012 16:47:57 -0300 Luiz Capitulino <lcapitulino@redhat.com> wrote: > This makes it possible for QEMU to use transparent huge pages (THP) > when transparent_hugepage/enabled=madvise. Otherwise THP is only > used when it's enabled system wide. > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> ping? > --- > exec.c | 1 + > osdep.h | 5 +++++ > 2 files changed, 6 insertions(+) > > diff --git a/exec.c b/exec.c > index 1114a09..7504909 100644 > --- a/exec.c > +++ b/exec.c > @@ -2584,6 +2584,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); > > qemu_ram_setup_dump(new_block->host, size); > + qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE); > > if (kvm_enabled()) > kvm_setup_guest_memory(new_block->host, size); > diff --git a/osdep.h b/osdep.h > index cb213e0..c5fd3d9 100644 > --- a/osdep.h > +++ b/osdep.h > @@ -108,6 +108,11 @@ void qemu_vfree(void *ptr); > #else > #define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID > #endif > +#ifdef MADV_HUGEPAGE > +#define QEMU_MADV_HUGEPAGE MADV_HUGEPAGE > +#else > +#define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID > +#endif > > #elif defined(CONFIG_POSIX_MADVISE) > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations 2012-10-15 18:57 ` Luiz Capitulino @ 2012-10-15 21:14 ` Michael Tokarev 2012-10-21 3:46 ` Aurelien Jarno 1 sibling, 0 replies; 5+ messages in thread From: Michael Tokarev @ 2012-10-15 21:14 UTC (permalink / raw) To: Luiz Capitulino; +Cc: aarcange, jan.kiszka, aliguori, qemu-devel On 15.10.2012 22:57, Luiz Capitulino wrote: > On Fri, 5 Oct 2012 16:47:57 -0300 > Luiz Capitulino <lcapitulino@redhat.com> wrote: > >> This makes it possible for QEMU to use transparent huge pages (THP) >> when transparent_hugepage/enabled=madvise. Otherwise THP is only >> used when it's enabled system wide. >> >> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > ping? > >> --- >> exec.c | 1 + >> osdep.h | 5 +++++ >> 2 files changed, 6 insertions(+) >> >> diff --git a/exec.c b/exec.c >> index 1114a09..7504909 100644 >> --- a/exec.c >> +++ b/exec.c >> @@ -2584,6 +2584,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, >> cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); >> >> qemu_ram_setup_dump(new_block->host, size); >> + qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE); FWIW, there was another attempt to do something like this: https://lists.gnu.org/archive/html/qemu-devel/2012-08/msg02870.html I'm not sure it is right or not, I just tried to guess, but that one also went unanswered. Maybe you will have better luck. Thanks, /mjt ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations 2012-10-15 18:57 ` Luiz Capitulino 2012-10-15 21:14 ` Michael Tokarev @ 2012-10-21 3:46 ` Aurelien Jarno 2012-10-22 13:50 ` Luiz Capitulino 1 sibling, 1 reply; 5+ messages in thread From: Aurelien Jarno @ 2012-10-21 3:46 UTC (permalink / raw) To: Luiz Capitulino; +Cc: aarcange, jan.kiszka, aliguori, qemu-devel On Mon, Oct 15, 2012 at 03:57:54PM -0300, Luiz Capitulino wrote: > On Fri, 5 Oct 2012 16:47:57 -0300 > Luiz Capitulino <lcapitulino@redhat.com> wrote: > > > This makes it possible for QEMU to use transparent huge pages (THP) > > when transparent_hugepage/enabled=madvise. Otherwise THP is only > > used when it's enabled system wide. > > > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > ping? > > > --- > > exec.c | 1 + > > osdep.h | 5 +++++ > > 2 files changed, 6 insertions(+) > > > > diff --git a/exec.c b/exec.c > > index 1114a09..7504909 100644 > > --- a/exec.c > > +++ b/exec.c > > @@ -2584,6 +2584,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > > cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); > > > > qemu_ram_setup_dump(new_block->host, size); > > + qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE); > > > > if (kvm_enabled()) > > kvm_setup_guest_memory(new_block->host, size); > > diff --git a/osdep.h b/osdep.h > > index cb213e0..c5fd3d9 100644 > > --- a/osdep.h > > +++ b/osdep.h > > @@ -108,6 +108,11 @@ void qemu_vfree(void *ptr); > > #else > > #define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID > > #endif > > +#ifdef MADV_HUGEPAGE > > +#define QEMU_MADV_HUGEPAGE MADV_HUGEPAGE > > +#else > > +#define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID > > +#endif > > > > #elif defined(CONFIG_POSIX_MADVISE) > > > I don't know this part of QEMU very well, so I tried to compare with how it was done for KSM. I found two main differences: - In the case of -mem-path QEMU doesn't try to mark the pages as mergeable. - An option (-machine mem-merge=false/true) is provided to enable KSM, defaulting to true. I am not sure if it makes sense for hugepages, but providing a mem-huge=false/true defaulting to true might be a good idea. -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurelien@aurel32.net http://www.aurel32.net ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations 2012-10-21 3:46 ` Aurelien Jarno @ 2012-10-22 13:50 ` Luiz Capitulino 0 siblings, 0 replies; 5+ messages in thread From: Luiz Capitulino @ 2012-10-22 13:50 UTC (permalink / raw) To: Aurelien Jarno; +Cc: aarcange, jan.kiszka, aliguori, qemu-devel, Avi Kivity On Sun, 21 Oct 2012 05:46:25 +0200 Aurelien Jarno <aurelien@aurel32.net> wrote: > On Mon, Oct 15, 2012 at 03:57:54PM -0300, Luiz Capitulino wrote: > > On Fri, 5 Oct 2012 16:47:57 -0300 > > Luiz Capitulino <lcapitulino@redhat.com> wrote: > > > > > This makes it possible for QEMU to use transparent huge pages (THP) > > > when transparent_hugepage/enabled=madvise. Otherwise THP is only > > > used when it's enabled system wide. > > > > > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > > > ping? > > > > > --- > > > exec.c | 1 + > > > osdep.h | 5 +++++ > > > 2 files changed, 6 insertions(+) > > > > > > diff --git a/exec.c b/exec.c > > > index 1114a09..7504909 100644 > > > --- a/exec.c > > > +++ b/exec.c > > > @@ -2584,6 +2584,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host, > > > cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff); > > > > > > qemu_ram_setup_dump(new_block->host, size); > > > + qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE); > > > > > > if (kvm_enabled()) > > > kvm_setup_guest_memory(new_block->host, size); > > > diff --git a/osdep.h b/osdep.h > > > index cb213e0..c5fd3d9 100644 > > > --- a/osdep.h > > > +++ b/osdep.h > > > @@ -108,6 +108,11 @@ void qemu_vfree(void *ptr); > > > #else > > > #define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID > > > #endif > > > +#ifdef MADV_HUGEPAGE > > > +#define QEMU_MADV_HUGEPAGE MADV_HUGEPAGE > > > +#else > > > +#define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID > > > +#endif > > > > > > #elif defined(CONFIG_POSIX_MADVISE) > > > > > > > I don't know this part of QEMU very well, so I tried to compare with how > it was done for KSM. I found two main differences: > - In the case of -mem-path QEMU doesn't try to mark the pages as > mergeable. As I wasn't completely sure that I could mark hugetlbfs areas as mergeable, I skipped them. Also, _iirc_ I based my patch on a RHEL patch by Andrea that did the same thing. Needless to say, but it's trivial to also mark hugetlbfs as mergeable if we want to. Now, marking hugetlbfs areas as HUGEPAGE seems definitely wrong. But would be nice if any of the CC'ed people could clarify these details. > - An option (-machine mem-merge=false/true) is provided to enable KSM, > defaulting to true. > > I am not sure if it makes sense for hugepages, but providing a > mem-huge=false/true defaulting to true might be a good idea. I thought about doing that, but went with a simpler version to get the discussion started... ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2012-10-22 14:48 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-10-05 19:47 [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations Luiz Capitulino 2012-10-15 18:57 ` Luiz Capitulino 2012-10-15 21:14 ` Michael Tokarev 2012-10-21 3:46 ` Aurelien Jarno 2012-10-22 13:50 ` Luiz Capitulino
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