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| author | Keqian Zhu <zhukeqian1@huawei.com> | 2020-12-17 09:49:40 +0800 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-03-06 11:41:54 +0100 |
| commit | e0a8f99355c32b48c9ef867127075b5267ae23d8 (patch) | |
| tree | 3c750b728cdffacbaca86499a77b8848d578f4d9 /accel/kvm | |
| parent | 10b6ee1616f984c1889d0851226a9ff14b35ac58 (diff) | |
| download | qemu-e0a8f99355c32b48c9ef867127075b5267ae23d8.zip qemu-e0a8f99355c32b48c9ef867127075b5267ae23d8.tar.gz qemu-e0a8f99355c32b48c9ef867127075b5267ae23d8.tar.bz2 | |
accel: kvm: Fix memory waste under mismatch page size
When handle dirty log, we face qemu_real_host_page_size and
TARGET_PAGE_SIZE. The first one is the granule of KVM dirty
bitmap, and the second one is the granule of QEMU dirty bitmap.
As qemu_real_host_page_size >= TARGET_PAGE_SIZE (kvm_init()
enforced it), misuse TARGET_PAGE_SIZE to init kvmslot dirty_bmap
may waste memory. For example, when qemu_real_host_page_size is
64K and TARGET_PAGE_SIZE is 4K, it wastes 93.75% (15/16) memory.
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <20201217014941.22872-2-zhukeqian1@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'accel/kvm')
| -rw-r--r-- | accel/kvm/kvm-all.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 84c943f..ffce83f 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -598,8 +598,12 @@ static void kvm_memslot_init_dirty_bitmap(KVMSlot *mem) * too, in most cases). * So for now, let's align to 64 instead of HOST_LONG_BITS here, in * a hope that sizeof(long) won't become >8 any time soon. + * + * Note: the granule of kvm dirty log is qemu_real_host_page_size. + * And mem->memory_size is aligned to it (otherwise this mem can't + * be registered to KVM). */ - hwaddr bitmap_size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS), + hwaddr bitmap_size = ALIGN(mem->memory_size / qemu_real_host_page_size, /*HOST_LONG_BITS*/ 64) / 8; mem->dirty_bmap = g_malloc0(bitmap_size); } |