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virtio-mem: Correct default THP size for ARM64

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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>
Message-id: 20220111063329.74447-2-gshan@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Gavin Shan 2022-01-11 14:33:28 +08:00 • committed by Peter Maydell
parent 87f14eaa51
commit 1263615efe
1 changed files with 20 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

32
hw/virtio/virtio-mem.c
View file

@ -46,14 +46,25 @@
*/ */
#define VIRTIO_MEM_MIN_BLOCK_SIZE ((uint32_t)(1 * MiB)) #define VIRTIO_MEM_MIN_BLOCK_SIZE ((uint32_t)(1 * MiB))
#if defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) || \ static uint32_t virtio_mem_default_thp_size(void)
defined(__powerpc64__) {
#define VIRTIO_MEM_DEFAULT_THP_SIZE ((uint32_t)(2 * MiB)) uint32_t default_thp_size = VIRTIO_MEM_MIN_BLOCK_SIZE;
#else
/* fallback to 1 MiB (e.g., the THP size on s390x) */ #if defined(__x86_64__) || defined(__arm__) || defined(__powerpc64__)
#define VIRTIO_MEM_DEFAULT_THP_SIZE VIRTIO_MEM_MIN_BLOCK_SIZE 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 #endif
return default_thp_size;
}
/* /*
* We want to have a reasonable default block size such that * We want to have a reasonable default block size such that
* 1. We avoid splitting THPs when unplugging memory, which degrades * 1. We avoid splitting THPs when unplugging memory, which degrades
@ -86,11 +97,8 @@ static uint32_t virtio_mem_thp_size(void)
if (g_file_get_contents(HPAGE_PMD_SIZE_PATH, &content, NULL, NULL) && if (g_file_get_contents(HPAGE_PMD_SIZE_PATH, &content, NULL, NULL) &&
!qemu_strtou64(content, &endptr, 0, &tmp) && !qemu_strtou64(content, &endptr, 0, &tmp) &&
(!endptr || *endptr == '\n')) { (!endptr || *endptr == '\n')) {
/* /* Sanity-check the value and fallback to something reasonable. */
* Sanity-check the value, if it's too big (e.g., aarch64 with 64k base if (!tmp || !is_power_of_2(tmp)) {
* pages) or weird, fallback to something smaller.
*/
if (!tmp || !is_power_of_2(tmp) || tmp > 16 * MiB) {
warn_report("Read unsupported THP size: %" PRIx64, tmp); warn_report("Read unsupported THP size: %" PRIx64, tmp);
} else { } else {
thp_size = tmp; thp_size = tmp;
@ -98,7 +106,7 @@ static uint32_t virtio_mem_thp_size(void)
} }
if (!thp_size) { 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 warn_report("Could not detect THP size, falling back to %" PRIx64
" MiB.", thp_size / MiB); " MiB.", thp_size / MiB);
} }