Add helpers to gather cache info from the host at init-time.
For now, only export the host's I/D cache line sizes, which we
will use to improve cache locality to avoid false sharing.
Suggested-by: Richard Henderson <r...@twiddle.net>
Suggested-by: Geert Martin Ijewski <gm.ijew...@web.de>
Tested-by: Geert Martin Ijewski <gm.ijew...@web.de>
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
include/qemu/osdep.h | 3 +
util/Makefile.objs | 1 +
util/cacheinfo.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 162 insertions(+)
create mode 100644 util/cacheinfo.c
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 1c9f5e2..ee43521 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -470,4 +470,7 @@ char *qemu_get_pid_name(pid_t pid);
*/
pid_t qemu_fork(Error **errp);
+extern int qemu_icache_linesize;
+extern int qemu_dcache_linesize;
+
#endif
diff --git a/util/Makefile.objs b/util/Makefile.objs
index c6205eb..94d9477 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -20,6 +20,7 @@ util-obj-y += host-utils.o
util-obj-y += bitmap.o bitops.o hbitmap.o
util-obj-y += fifo8.o
util-obj-y += acl.o
+util-obj-y += cacheinfo.o
util-obj-y += error.o qemu-error.o
util-obj-y += id.o
util-obj-y += iov.o qemu-config.o qemu-sockets.o uri.o notify.o
diff --git a/util/cacheinfo.c b/util/cacheinfo.c
new file mode 100644
index 0000000..41dccb1
--- /dev/null
+++ b/util/cacheinfo.c
@@ -0,0 +1,158 @@
+/*
+ * cacheinfo.c - helpers to query the host about its caches
+ *
+ * Copyright (C) 2017, Emilio G. Cota <c...@braap.org>
+ * License: GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+int qemu_icache_linesize = 64;
+int qemu_dcache_linesize = 64;
+
+#ifdef _WIN32
+static unsigned int linesize_win(PROCESSOR_CACHE_TYPE type)
+{
+ PSYSTEM_LOGICAL_PROCESSOR_INFORMATION buf;
+ DWORD size = 0;
+ unsigned int ret = 0;
+ BOOL success;
+ size_t n;
+ size_t i;
+
+ success = GetLogicalProcessorInformation(0, &size);
+ if (success || GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+ return 0;
+ }
+ buf = (PSYSTEM_LOGICAL_PROCESSOR_INFORMATION)g_malloc0(size);
+ if (!GetLogicalProcessorInformation(buf, &size)) {
+ goto out;
+ }
+
+ n = size / sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
+ for (i = 0; i < n; i++) {
+ if (buf[i].Relationship == RelationCache &&
+ buf[i].Cache.Level == 1 &&
+ (buf[i].Cache.Type == CacheUnified ||
+ buf[i].Cache.Type == type)) {
+ ret = buf[i].Cache.LineSize;
+ break;
+ }
+ }
+ out:
+ g_free(buf);
+ return ret;
+}
+#endif
+
+#ifdef __APPLE__
+#include <sys/sysctl.h>
+
+unsigned int linesize_apple(void)
+{
+ unsigned long bytes;
+ size_t len = sizeof(bytes);
+
+ /* There's only a single sysctl for both I/D cache line sizes */
+ if (sysctlbyname("hw.cachelinesize", &bytes, &len, NULL, 0)) {
+ return 0;
+ }
+ return bytes;
+}
+#endif
+
+static void icache_info(void)
+{
+ #ifdef _SC_LEVEL1_ICACHE_LINESIZE
+ {
+ long x = sysconf(_SC_LEVEL1_ICACHE_LINESIZE);
+
+ if (x > 0) {
+ qemu_icache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef AT_ICACHEBSIZE
+ /* glibc does not always export this through sysconf, e.g. on PPC */
+ {
+ unsigned long x = qemu_getauxval(AT_ICACHEBSIZE);
+
+ if (x > 0) {
+ qemu_icache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef _WIN32
+ {
+ unsigned int x = linesize_win(CacheInstruction);
+
+ if (x > 0) {
+ qemu_icache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef __APPLE__
+ {
+ unsigned int x = linesize_apple();
+
+ if (x > 0) {
+ qemu_icache_linesize = x;
+ return;
+ }
+ }
+ #endif
+}
+
+static void dcache_info(void)
+{
+ #ifdef _SC_LEVEL1_DCACHE_LINESIZE
+ {
+ long x = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
+
+ if (x > 0) {
+ qemu_dcache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef AT_DCACHEBSIZE
+ {
+ unsigned long x = qemu_getauxval(AT_DCACHEBSIZE);
+
+ if (x > 0) {
+ qemu_dcache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef _WIN32
+ {
+ unsigned int x = linesize_win(CacheData);
+
+ if (x > 0) {
+ qemu_dcache_linesize = x;
+ return;
+ }
+ }
+ #endif
+ #ifdef __APPLE__
+ {
+ unsigned int x = linesize_apple();
+
+ if (x > 0) {
+ qemu_dcache_linesize = x;
+ return;
+ }
+ }
+ #endif
+}
+
+static void __attribute__((constructor)) cacheinfo_init(void)
+{
+ icache_info();
+ dcache_info();
+}
--
2.7.4
