tests: Stabilize block rate limiter workloads

Add a ramp time before measuring the block rate limiter tests so
both the single device and group workloads are measured after
warm up to make the measurements less sensitive to startup
transients.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

Author: weltling

cloud-hypervisor/tests/integration.rs

@@ -10477,6 +10477,7 @@ mod rate_limiter {
 
     const NET_RATE_LIMITER_RUNTIME: u32 = 20;
     const BLOCK_RATE_LIMITER_RUNTIME: u32 = 20;
+    const BLOCK_RATE_LIMITER_RAMP_TIME: u32 = 5;
 
     // Check if the 'measured' rate is within the expected 'difference' (in percentage)
     // compared to given 'limit' rate.
@@ -10624,7 +10625,8 @@ mod rate_limiter {
             let fio_command = format!(
                 "sudo fio --filename=/dev/vdc --name=test --output-format=json \
                 --direct=1 --bs=4k --ioengine=io_uring --iodepth=64 \
-                --rw={fio_ops} --runtime={BLOCK_RATE_LIMITER_RUNTIME} --numjobs={num_queues}"
+                --rw={fio_ops} --runtime={BLOCK_RATE_LIMITER_RUNTIME} \
+                --ramp_time={BLOCK_RATE_LIMITER_RAMP_TIME} --numjobs={num_queues}",
             );
             let output = guest.ssh_command(&fio_command).unwrap();
 
@@ -10721,7 +10723,8 @@ mod rate_limiter {
             let mut fio_command = format!(
                 "sudo fio --name=global --output-format=json \
                 --direct=1 --bs=4k --ioengine=io_uring --iodepth=64 \
-                --rw={fio_ops} --runtime={BLOCK_RATE_LIMITER_RUNTIME} --numjobs={num_queues}"
+                --rw={fio_ops} --runtime={BLOCK_RATE_LIMITER_RUNTIME} \
+                --ramp_time={BLOCK_RATE_LIMITER_RAMP_TIME} --numjobs={num_queues}",
             );
 
             // Generate additional argument for each disk: