From 1263615efe51e5f1f38f4818f0de88abc33b49a6 Mon Sep 17 00:00:00 2001 From: Gavin Shan Date: Tue, 11 Jan 2022 14:33:28 +0800 Subject: [PATCH] virtio-mem: Correct default THP size for ARM64 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 Signed-off-by: Gavin Shan Reviewed-by: Jonathan Cameron Reviewed-by: David Hildenbrand Message-id: 20220111063329.74447-2-gshan@redhat.com Signed-off-by: Peter Maydell --- 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 04c223b0c9..1ca45336dc 100644 --- a/hw/virtio/virtio-mem.c +++ b/hw/virtio/virtio-mem.c @@ -46,14 +46,25 @@ */ #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 @@ -86,11 +97,8 @@ 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; @@ -98,7 +106,7 @@ 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); } -- 2.30.2