On 9/27/19 7:04 AM, Douglas Gilbert wrote:
Add an option to use the given command delay (in nanoseconds)
as the upper limit for command durations. A pseudo random
number generator chooses each duration from the range:
[0..delay_in_ns)
Main benefit: allows testing with out-of-order responses.
Please clarify which code you want to test. I think out-of-order
response handling in the SCSI core and block layer core is already being
triggered by many storage workloads.
@@ -4354,9 +4357,21 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
ktime_t kt;
if (delta_jiff > 0) {
- kt = ns_to_ktime((u64)delta_jiff * (NSEC_PER_SEC / HZ));
- } else
- kt = ndelay;
+ u64 ns = (u64)delta_jiff * (NSEC_PER_SEC / HZ);
Has it been considered to use jiffies_to_nsecs() instead of open-coding
that function?
+ if (sdebug_random && ns < U32_MAX) {
+ ns = prandom_u32_max((u32)ns);
+ } else if (sdebug_random) {
+ ns >>= 10; /* divide by 1024 */
+ if (ns < U32_MAX) /* an hour and a bit */
+ ns = prandom_u32_max((u32)ns);
+ ns <<= 10;
+ }
+ kt = ns_to_ktime(ns);
Is it really necessary to use nanosecond resolution? Can the above code
be simplified by using microseconds as time unit instead of nanoseconds?
+MODULE_PARM_DESC(random, "1-> command duration chosen from [0..delay_in_ns) (def=0)");
Would this description become more clear if it would be changed into
something like the following: "If set, uniformly randomize command
duration between 0 and delay_in_ns" ?
+static ssize_t random_show(struct device_driver *ddp, char *buf)
+{
+ return scnprintf(buf, PAGE_SIZE, "%d\n", sdebug_random ? 1 : 0);
+}
Since sdebug_random is either 0 or 1, is the "? 1 : 0" part necessary?
+static ssize_t random_store(struct device_driver *ddp, const char *buf,
+ size_t count)
+{
+ int n;
+
+ if (count > 0 && 1 == sscanf(buf, "%d", &n) && n >= 0) {
+ sdebug_random = (n > 0);
+ return count;
+ }
+ return -EINVAL;
+}
Has this patch been verified with checkpatch? I'm asking since
checkpatch should complain about "1 == sscanf(...)". See also commit
c5595fa2f1ce ("checkpatch: add constant comparison on left side test").
@@ -5338,7 +5373,7 @@ static int __init scsi_debug_init(void)
dif_size = sdebug_store_sectors * sizeof(struct t10_pi_tuple);
dif_storep = vmalloc(dif_size);
- pr_err("dif_storep %u bytes @ %p\n", dif_size, dif_storep);
+ pr_err("dif_storep %u bytes @ %pK\n", dif_size, dif_storep);
if (dif_storep == NULL) {
pr_err("out of mem. (DIX)\n");
Is it useful to print the kernel pointer 'dif_storep'?
Thanks,
Bart.
