@@ -34,6 +34,8 @@
#define CREATE_TRACE_POINTS
#include "trace.h"
+static uint __read_mostly max_alloc_try_dpages = 1;
+
struct dmemfs_mount_opts {
unsigned long dpage_size;
};
@@ -46,6 +48,44 @@ enum dmemfs_param {
Opt_dpagesize,
};
+static int
+max_alloc_try_dpages_set(const char *val, const struct kernel_param *kp)
+{
+ uint sval;
+ int ret;
+
+ ret = kstrtouint(val, 0, &sval);
+ if (ret)
+ return ret;
+
+ /* should be 1 at least */
+ if (!sval)
+ return -EINVAL;
+
+ max_alloc_try_dpages = sval;
+ return 0;
+}
+
+static struct kernel_param_ops alloc_max_try_dpages_ops = {
+ .set = max_alloc_try_dpages_set,
+ .get = param_get_uint,
+};
+
+/*
+ * it specifies the dmem page number allocated at one time, then
+ * multiple radix entries can be created. That will relief the
+ * allocation pressure and make page fault more fast.
+ *
+ * however that could cause no dmem page mmapped to userspace
+ * even if there are some free dmem pages
+ *
+ * set it to 1 to completely disable this behavior
+ */
+fs_param_cb(max_alloc_try_dpages, &alloc_max_try_dpages_ops,
+ &max_alloc_try_dpages, 0644);
+__MODULE_PARM_TYPE(max_alloc_try_dpages, "uint");
+MODULE_PARM_DESC(max_alloc_try_dpages, "Set the dmem page number allocated at one time, should be 1 at least");
+
const struct fs_parameter_spec dmemfs_fs_parameters[] = {
fsparam_string("pagesize", Opt_dpagesize),
{}
@@ -314,6 +354,7 @@ static void *find_radix_entry_or_next(struct address_space *mapping,
}
rcu_read_unlock();
+ try_dpages = min(try_dpages, max_alloc_try_dpages);
/* entry does not exist, create it */
addr = dmem_alloc_pages_vma(vma, fault_addr, try_dpages, &dpages);
if (!addr) {