From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:56594) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TPmUm-0004fn-Ob for qemu-devel@nongnu.org; Sat, 20 Oct 2012 23:46:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TPmUl-0004iU-Ju for qemu-devel@nongnu.org; Sat, 20 Oct 2012 23:46:36 -0400 Received: from hall.aurel32.net ([88.191.126.93]:47953) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TPmUl-0004iH-Dh for qemu-devel@nongnu.org; Sat, 20 Oct 2012 23:46:35 -0400 Date: Sun, 21 Oct 2012 05:46:25 +0200 From: Aurelien Jarno Message-ID: <20121021034625.GD5261@ohm.aurel32.net> References: <20121005164758.4808b2d1@doriath.home> <20121015155754.54f11e01@doriath.home> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20121015155754.54f11e01@doriath.home> Subject: Re: [Qemu-devel] [PATCH] Call MADV_HUGEPAGE for guest RAM allocations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: aarcange@redhat.com, jan.kiszka@siemens.com, aliguori@us.ibm.com, 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 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 > > 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