| Message ID | 20181220152126.18741-2-julien.grall@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm: Allow the user to specify where the RAM is placed in the memory | expand |
Julien, On 20/12/2018 15:21, Julien Grall wrote: > From: Suzuki K Poulose <suzuki.poulose@arm.com> > > With 16K pagesize, the hugepage size is 32M. Align the guest > memory to the hugepagesize for 16K. > > Cc: Marc Zyngier <marc.zyngier@arm.com> > Cc: Andre Przywara <andre.przywara@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> > Signed-off-by: Julien Grall <julien.grall@arm.com> > --- > arm/kvm.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arm/kvm.c b/arm/kvm.c > index b824f63..5b1f73c 100644 > --- a/arm/kvm.c > +++ b/arm/kvm.c > @@ -59,14 +59,22 @@ void kvm__arch_set_cmdline(char *cmdline, bool video) > > void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size) > { > + unsigned long alignment; > + > /* > * Allocate guest memory. We must align our buffer to 64K to > * correlate with the maximum guest page size for virtio-mmio. > * If using THP, then our minimal alignment becomes 2M. > * 2M trumps 64K, so let's go with that. > + * If we are running with 16K page size, align the memory to > + * 32M, so that we can make use of the THP. > */ One issue that I realized with the above adjustment is when we specify a hugetlbfs path, e.g, 1GB hugepages with 4K (with recently added PUD huge page support at Stage2), we fail to allocate memory. I think the whole alignment game should be performed only for the anon_mmap case. If the hugetlbfs path is specified, we are guaranteed to get aligned memory banks. Do you think you could fix it with this series (of course as a separate patch), as it seems more relevant ? You could may be do : if (!hugetlbfs_path) { > + if (sysconf(_SC_PAGESIZE) == SZ_16K) > + alignment = SZ_32M; > + else > + alignment = SZ_2M; } else { alignment = 0; } > kvm->ram_size = min(ram_size, (u64)ARM_MAX_MEMORY(kvm)); > - kvm->arch.ram_alloc_size = kvm->ram_size + SZ_2M; > + kvm->arch.ram_alloc_size = kvm->ram_size + alignment; > kvm->arch.ram_alloc_start = mmap_anon_or_hugetlbfs(kvm, hugetlbfs_path, > kvm->arch.ram_alloc_size); > > @@ -75,7 +83,7 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size) > kvm->arch.ram_alloc_size, errno); > > kvm->ram_start = (void *)ALIGN((unsigned long)kvm->arch.ram_alloc_start, > - SZ_2M); > + alignment); Cheers Suzuki
diff --git a/arm/kvm.c b/arm/kvm.c index b824f63..5b1f73c 100644 --- a/arm/kvm.c +++ b/arm/kvm.c @@ -59,14 +59,22 @@ void kvm__arch_set_cmdline(char *cmdline, bool video) void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size) { + unsigned long alignment; + /* * Allocate guest memory. We must align our buffer to 64K to * correlate with the maximum guest page size for virtio-mmio. * If using THP, then our minimal alignment becomes 2M. * 2M trumps 64K, so let's go with that. + * If we are running with 16K page size, align the memory to + * 32M, so that we can make use of the THP. */ + if (sysconf(_SC_PAGESIZE) == SZ_16K) + alignment = SZ_32M; + else + alignment = SZ_2M; kvm->ram_size = min(ram_size, (u64)ARM_MAX_MEMORY(kvm)); - kvm->arch.ram_alloc_size = kvm->ram_size + SZ_2M; + kvm->arch.ram_alloc_size = kvm->ram_size + alignment; kvm->arch.ram_alloc_start = mmap_anon_or_hugetlbfs(kvm, hugetlbfs_path, kvm->arch.ram_alloc_size); @@ -75,7 +83,7 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size) kvm->arch.ram_alloc_size, errno); kvm->ram_start = (void *)ALIGN((unsigned long)kvm->arch.ram_alloc_start, - SZ_2M); + alignment); madvise(kvm->arch.ram_alloc_start, kvm->arch.ram_alloc_size, MADV_MERGEABLE);