Given the use of the number of CPU's for sizing would this play nice
with hot plug CPU's?
Regards
Steve
On 05/01/2017 01:44, Mark Johnston wrote:
Author: markj
Date: Thu Jan 5 01:44:12 2017
New Revision: 311346
URL: https://svnweb.freebsd.org/changeset/base/311346
Log:
Add a small allocator for exec_map entries.
Upon each execve, we allocate a KVA range for use in copying data to the
new image. Pages must be faulted into the range, and when the range is
freed, the backing pages are freed and their mappings are destroyed. This
is a lot of needless overhead, and the exec_map management becomes a
bottleneck when many CPUs are executing execve concurrently. Moreover, the
number of available ranges is fixed at 16, which is insufficient on large
systems and potentially excessive on 32-bit systems.
The new allocator reduces overhead by making exec_map allocations
persistent. When a range is freed, pages backing the range are marked clean
and made easy to reclaim. With this change, the exec_map is sized based on
the number of CPUs.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D8921
Modified:
head/sys/kern/kern_exec.c
head/sys/sys/imgact.h
head/sys/vm/vm_init.c
head/sys/vm/vm_kern.c
head/sys/vm/vm_kern.h
Modified: head/sys/kern/kern_exec.c
==
--- head/sys/kern/kern_exec.c Thu Jan 5 01:28:08 2017(r311345)
+++ head/sys/kern/kern_exec.c Thu Jan 5 01:44:12 2017(r311346)
@@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
#include
#include
#include
+#include
#include
#include
#include
@@ -59,6 +60,7 @@ __FBSDID("$FreeBSD$");
#include
#include
#include
+#include
#include
#include
#include
@@ -1315,17 +1317,80 @@ err_exit:
return (error);
}
+struct exec_args_kva {
+ vm_offset_t addr;
+ SLIST_ENTRY(exec_args_kva) next;
+};
+
+static DPCPU_DEFINE(struct exec_args_kva *, exec_args_kva);
+
+static SLIST_HEAD(, exec_args_kva) exec_args_kva_freelist;
+static struct mtx exec_args_kva_mtx;
+
+static void
+exec_prealloc_args_kva(void *arg __unused)
+{
+ struct exec_args_kva *argkva;
+ u_int i;
+
+ SLIST_INIT(&exec_args_kva_freelist);
+ mtx_init(&exec_args_kva_mtx, "exec args kva", NULL, MTX_DEF);
+ for (i = 0; i < exec_map_entries; i++) {
+ argkva = malloc(sizeof(*argkva), M_PARGS, M_WAITOK);
+ argkva->addr = kmap_alloc_wait(exec_map, exec_map_entry_size);
+ SLIST_INSERT_HEAD(&exec_args_kva_freelist, argkva, next);
+ }
+}
+SYSINIT(exec_args_kva, SI_SUB_EXEC, SI_ORDER_ANY, exec_prealloc_args_kva,
NULL);
+
+static vm_offset_t
+exec_alloc_args_kva(void **cookie)
+{
+ struct exec_args_kva *argkva;
+
+ argkva = (void *)atomic_readandclear_ptr(
+ (uintptr_t *)DPCPU_PTR(exec_args_kva));
+ if (argkva == NULL) {
+ mtx_lock(&exec_args_kva_mtx);
+ while ((argkva = SLIST_FIRST(&exec_args_kva_freelist)) == NULL)
+ (void)mtx_sleep(&exec_args_kva_freelist,
+ &exec_args_kva_mtx, 0, "execkva", 0);
+ SLIST_REMOVE_HEAD(&exec_args_kva_freelist, next);
+ mtx_unlock(&exec_args_kva_mtx);
+ }
+ *(struct exec_args_kva **)cookie = argkva;
+ return (argkva->addr);
+}
+
+static void
+exec_free_args_kva(void *cookie)
+{
+ struct exec_args_kva *argkva;
+ vm_offset_t base;
+
+ argkva = cookie;
+ base = argkva->addr;
+
+ vm_map_madvise(exec_map, base, base + exec_map_entry_size, MADV_FREE);
+ if (!atomic_cmpset_ptr((uintptr_t *)DPCPU_PTR(exec_args_kva),
+ (uintptr_t)NULL, (uintptr_t)argkva)) {
+ mtx_lock(&exec_args_kva_mtx);
+ SLIST_INSERT_HEAD(&exec_args_kva_freelist, argkva, next);
+ wakeup_one(&exec_args_kva_freelist);
+ mtx_unlock(&exec_args_kva_mtx);
+ }
+}
+
/*
* Allocate temporary demand-paged, zero-filled memory for the file name,
- * argument, and environment strings. Returns zero if the allocation succeeds
- * and ENOMEM otherwise.
+ * argument, and environment strings.
*/
int
exec_alloc_args(struct image_args *args)
{
- args->buf = (char *)kmap_alloc_wait(exec_map, PATH_MAX + ARG_MAX);
- return (args->buf != NULL ? 0 : ENOMEM);
+ args->buf = (char *)exec_alloc_args_kva(&args->bufkva);
+ return (0);
}
void
@@ -1333,8 +1398,7 @@ exec_free_args(struct image_args *args)
{
if (args->buf != NULL) {
- kmap_free_wakeup(exec_map, (vm_offset_t)args->buf,
- PATH_MAX + ARG_MAX);
+ exec_free_args_kva(args->bufkva);
args->buf = NULL;
}
if (args->fname_buf != NULL) {
Modified: head/sys/sys/imgact.h
===
