From b6c45f5ea5d1a379ac0a507cf59345c573b27cc8 Mon Sep 17 00:00:00 2001 From: Chuan Zheng Date: Wed, 9 Feb 2022 14:21:39 +0800 Subject: [PATCH] oslib-posix: optimise vm startup time for 1G hugepage It takes quit a long time to clear 1G-hugepage, which makes glibc pthread_create quit slow. Create touch_pages threads in advance, and then handle the touch_pages callback. Only read lock is held here. --- util/oslib-posix.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index e86fd64e09..9ca3fee2b8 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -88,6 +88,8 @@ static QemuMutex sigbus_mutex; static QemuMutex page_mutex; static QemuCond page_cond; +static int started_num_threads; + int qemu_get_thread_id(void) { #if defined(__linux__) @@ -344,6 +346,10 @@ static void *do_touch_pages(void *arg) } qemu_mutex_unlock(&page_mutex); + while (started_num_threads != memset_args->context.num_threads) { + smp_mb(); + } + /* unblock SIGBUS */ sigemptyset(&set); sigaddset(&set, SIGBUS); @@ -448,7 +454,7 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages, context.threads = g_new0(MemsetThread, context.num_threads); numpages_per_thread = numpages / context.num_threads; leftover = numpages % context.num_threads; - for (i = 0; i < context.num_threads; i++) { + for (i = 0, started_num_threads = 0; i < context.num_threads; i++) { context.threads[i].addr = addr; context.threads[i].numpages = numpages_per_thread + (i < leftover); context.threads[i].hpagesize = hpagesize; @@ -464,6 +470,7 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages, QEMU_THREAD_JOINABLE); } addr += context.threads[i].numpages * hpagesize; + started_num_threads++; } if (!use_madv_populate_write) { -- 2.27.0