From: Keqian Zhu <zhukeqian1@huawei.com>
To: Peter Maydell <peter.maydell@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Andrew Jones <drjones@redhat.com>, Peter Xu <peterx@redhat.com>
Cc: jiangkunkun@huawei.com, qemu-devel@nongnu.org,
qemu-arm@nongnu.org, Zenghui Yu <yuzenghui@huawei.com>,
wanghaibin.wang@huawei.com, Keqian Zhu <zhukeqian1@huawei.com>
Subject: [PATCH v2 1/2] accel: kvm: Fix memory waste under mismatch page size
Date: Thu, 17 Dec 2020 09:49:40 +0800 [thread overview]
Message-ID: <20201217014941.22872-2-zhukeqian1@huawei.com> (raw)
In-Reply-To: <20201217014941.22872-1-zhukeqian1@huawei.com>
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>
---
accel/kvm/kvm-all.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
---
v2
- Address Andrew's comment (qemu_real_host_page_size >= TARGET_PAGE_SIZE
is a rule).
- Add Andrew and Peter's R-b.
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 389eaace72..f6b16a8df8 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -620,8 +620,12 @@ 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);
}
--
2.23.0
next prev parent reply other threads:[~2020-12-17 1:53 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 1:49 [PATCH v2 0/2] accel: kvm: Some bugfixes for kvm dirty log Keqian Zhu
2020-12-17 1:49 ` Keqian Zhu [this message]
2020-12-17 1:49 ` [PATCH v2 2/2] accel: kvm: Add aligment assert for kvm_log_clear_one_slot Keqian Zhu
2020-12-17 12:18 ` Andrew Jones
2020-12-17 14:36 ` Peter Xu
2021-02-01 15:14 ` Philippe Mathieu-Daudé
2021-02-02 1:17 ` Keqian Zhu
2021-03-09 13:48 ` Thomas Huth
2021-03-09 14:05 ` Keqian Zhu
2021-03-09 14:45 ` Thomas Huth
2021-03-09 14:57 ` Dr. David Alan Gilbert
2021-03-09 16:08 ` Peter Xu
2021-03-10 1:57 ` Keqian Zhu
2021-03-09 16:20 ` Thomas Huth
2021-03-09 16:26 ` Peter Maydell
2021-03-09 19:03 ` Paolo Bonzini
2021-03-09 15:11 ` zhukeqian
2021-01-06 7:07 ` [PATCH v2 0/2] accel: kvm: Some bugfixes for kvm dirty log Keqian Zhu
2021-01-25 7:51 ` Keqian Zhu
2021-02-01 13:07 ` Keqian Zhu
2021-03-02 11:43 ` [PING] " Keqian Zhu
2021-03-02 13:14 ` Paolo Bonzini
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