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[PATCH v3 1/2] virtio-mem: Correct default THP size for ARM64
From: |
Gavin Shan |
Subject: |
[PATCH v3 1/2] virtio-mem: Correct default THP size for ARM64 |
Date: |
Sat, 4 Dec 2021 07:34:03 +0800 |
The default block size is same as to the THP size, which is either
retrieved from "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size"
or hardcoded to 2MB. There are flaws in both mechanisms and this
intends to fix them up.
* When "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size" is
used to getting the THP size, 32MB and 512MB are valid values
when we have 16KB and 64KB page size on ARM64.
* When the hardcoded THP size is used, 2MB, 32MB and 512MB are
valid values when we have 4KB, 16KB and 64KB page sizes on
ARM64.
Co-developed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
hw/virtio/virtio-mem.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index d5a578142b..b20595a496 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -38,14 +38,25 @@
*/
#define VIRTIO_MEM_MIN_BLOCK_SIZE ((uint32_t)(1 * MiB))
-#if defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) || \
- defined(__powerpc64__)
-#define VIRTIO_MEM_DEFAULT_THP_SIZE ((uint32_t)(2 * MiB))
-#else
- /* fallback to 1 MiB (e.g., the THP size on s390x) */
-#define VIRTIO_MEM_DEFAULT_THP_SIZE VIRTIO_MEM_MIN_BLOCK_SIZE
+static uint32_t virtio_mem_default_thp_size(void)
+{
+ uint32_t default_thp_size = VIRTIO_MEM_MIN_BLOCK_SIZE;
+
+#if defined(__x86_64__) || defined(__arm__) || defined(__powerpc64__)
+ default_thp_size = 2 * MiB;
+#elif defined(__aarch64__)
+ if (qemu_real_host_page_size == 4 * KiB) {
+ default_thp_size = 2 * MiB;
+ } else if (qemu_real_host_page_size == 16 * KiB) {
+ default_thp_size = 32 * MiB;
+ } else if (qemu_real_host_page_size == 64 * KiB) {
+ default_thp_size = 512 * MiB;
+ }
#endif
+ return default_thp_size;
+}
+
/*
* We want to have a reasonable default block size such that
* 1. We avoid splitting THPs when unplugging memory, which degrades
@@ -78,11 +89,8 @@ static uint32_t virtio_mem_thp_size(void)
if (g_file_get_contents(HPAGE_PMD_SIZE_PATH, &content, NULL, NULL) &&
!qemu_strtou64(content, &endptr, 0, &tmp) &&
(!endptr || *endptr == '\n')) {
- /*
- * Sanity-check the value, if it's too big (e.g., aarch64 with 64k base
- * pages) or weird, fallback to something smaller.
- */
- if (!tmp || !is_power_of_2(tmp) || tmp > 16 * MiB) {
+ /* Sanity-check the value and fallback to something reasonable. */
+ if (!tmp || !is_power_of_2(tmp)) {
warn_report("Read unsupported THP size: %" PRIx64, tmp);
} else {
thp_size = tmp;
@@ -90,7 +98,7 @@ static uint32_t virtio_mem_thp_size(void)
}
if (!thp_size) {
- thp_size = VIRTIO_MEM_DEFAULT_THP_SIZE;
+ thp_size = virtio_mem_default_thp_size();
warn_report("Could not detect THP size, falling back to %" PRIx64
" MiB.", thp_size / MiB);
}
--
2.23.0