From 89aec6411c429adb662c53c94a986a5397961a7f Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 17 Dec 2021 14:46:07 +0100 Subject: [PATCH] util/oslib-posix: Don't create too many threads with small memory or little pages MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Let's limit the number of threads to something sane, especially that - We don't have more threads than the number of pages we have - We don't have threads that initialize small (< 64 MiB) memory Reviewed-by: Pankaj Gupta Reviewed-by: Dr. David Alan Gilbert Reviewed-by: Daniel P. Berrangé Reviewed-by: Michal Privoznik Signed-off-by: David Hildenbrand Message-Id: <20211217134611.31172-5-david@redhat.com> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- util/oslib-posix.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/util/oslib-posix.c b/util/oslib-posix.c index cf2ead54ad..67c08a425e 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -40,6 +40,7 @@ #include #include "qemu/cutils.h" #include "qemu/compiler.h" +#include "qemu/units.h" #ifdef CONFIG_LINUX #include @@ -525,7 +526,8 @@ static void *do_madv_populate_write_pages(void *arg) return (void *)(uintptr_t)ret; } -static inline int get_memset_num_threads(int smp_cpus) +static inline int get_memset_num_threads(size_t hpagesize, size_t numpages, + int smp_cpus) { long host_procs = sysconf(_SC_NPROCESSORS_ONLN); int ret = 1; @@ -533,6 +535,12 @@ static inline int get_memset_num_threads(int smp_cpus) if (host_procs > 0) { ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus); } + + /* Especially with gigantic pages, don't create more threads than pages. */ + ret = MIN(ret, numpages); + /* Don't start threads to prealloc comparatively little memory. */ + ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB))); + /* In case sysconf() fails, we fall back to single threaded */ return ret; } @@ -542,7 +550,7 @@ static int touch_all_pages(char *area, size_t hpagesize, size_t numpages, { static gsize initialized = 0; MemsetContext context = { - .num_threads = get_memset_num_threads(smp_cpus), + .num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus), }; size_t numpages_per_thread, leftover; void *(*touch_fn)(void *);