Hi Xiao,

Xiao Ni [off-list ref] wrote:

quoted

Ali Gholami Rudi [off-list ref] wrote:

quoted

Xiao Ni [off-list ref] wrote:

quoted

Because it can be reproduced easily in your environment. Can you try
with the latest upstream kernel? If the problem doesn't exist with
latest upstream kernel. You can use git bisect to find which patch can
fix this problem.

I just tried the upstream.  I get almost the same result with 1G ramdisks.

Without RAID (writing to /dev/ram0)
READ:  IOPS=15.8M BW=60.3GiB/s
WRITE: IOPS= 6.8M BW=27.7GiB/s

RAID1 (writing to /dev/md/test)
READ:  IOPS=518K BW=2028MiB/s
WRITE: IOPS=222K BW= 912MiB/s

I can reproduce this with upstream kernel too.

RAID1
READ: bw=3699MiB/s (3879MB/s)
WRITE: bw=1586MiB/s (1663MB/s)

ram disk:
READ: bw=5720MiB/s (5997MB/s)
WRITE: bw=2451MiB/s (2570MB/s)

There is a performance problem. But not like your result. Your result
has a huge gap. I'm not sure the reason. Any thoughts?

It may be the number of cores; in my setup there are 128 cores (256
threads).  If I understand it correctly, the problem is that
wakeup(...->wait_barrier) is called unconditionally at the same time
by many cores in functions like allow_barrier and flush_bio_list,
while no task is waiting in the task queue.  This results in a
lock contention for wq_head->lock in __wakekup_common_lock().

quoted

And this is perf's output:

I'm not familiar with perf, what's your command that I can use to see
the same output?

perf record --call-graph dwarf fio fio.test

perf report

Thanks,
Ali