From e5fc3a755c9ba9f18bc0416c60f745912cb5b104 Mon Sep 17 00:00:00 2001 From: Chuan Zheng Date: Wed, 9 Feb 2022 14:21:39 +0800 Subject: [PATCH 15/15] 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 | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index e8bdb02e1d..18a38b9464 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -84,6 +84,7 @@ typedef struct MemsetThread MemsetThread; static MemsetThread *memset_thread; static int memset_num_threads; +static int started_num_threads; static bool memset_thread_failed; static QemuMutex page_mutex; @@ -464,6 +465,10 @@ static void *do_touch_pages(void *arg) } qemu_mutex_unlock(&page_mutex); + while (started_num_threads != memset_num_threads) { + smp_mb(); + } + /* unblock SIGBUS */ sigemptyset(&set); sigaddset(&set, SIGBUS); @@ -529,7 +534,7 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages, memset_thread = g_new0(MemsetThread, memset_num_threads); numpages_per_thread = numpages / memset_num_threads; leftover = numpages % memset_num_threads; - for (i = 0; i < memset_num_threads; i++) { + for (i = 0, started_num_threads = 0; i < memset_num_threads; i++) { memset_thread[i].addr = addr; memset_thread[i].numpages = numpages_per_thread + (i < leftover); memset_thread[i].hpagesize = hpagesize; @@ -537,6 +542,7 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages, do_touch_pages, &memset_thread[i], QEMU_THREAD_JOINABLE); addr += memset_thread[i].numpages * hpagesize; + started_num_threads++; } qemu_mutex_lock(&page_mutex); -- 2.27.0