On Sun, 26 Nov 2023 22:44:45 -0800
Christoph Hellwig [off-list ref] wrote:

Hi Shushu,

the work certainly l-ooks interesting!

However:

quoted

Optimized by using fine-grained locks, customized data structures,
and scattered address space. Achieves significant improvements in
both throughput and latency.

this is a lot of work for a single Linux patch, we usually do that
work pice by pice instead of complete rewrite, and for such
signigicant changes the commit logs also tend to be a bit extensive.

I'm also not quite sure what scattered address spaces are - I bet
reading the paper (I plan to get to that) would explain it, but it
also helps to explain the idea in the commit message.

That's my high level nitpicking for now, I'll try to read the paper
and the patch in detail and come back later.

Hi Everyone,

I went ahead and ran a series of performance tests on this patch to
help the community understand the value.Here's a summary of what have
completed and am happy to run some more to keep the patch moving.

I have not yet reviewed the code as I wanted to make sure it provided
good benefit first and it does for sure. I will be reviewing shortly.
Here is a summary of my tests:

* Kioxia CM7 drives
  https://americas.kioxia.com/content/dam/kioxia/shared/business/ssd/enterprise-ssd/asset/productbrief/eSSD-CM7-V-product-brief.pdf
* Dual Socket Xeon 8368 2.4GHz 256G RAM
* Results are the average of just 2 60 second runs per data point, if
  interest continues I can re-run to eliminate any potential anomalies
* I used 8 fio jobs per disk and 2 group_thread_cnt per disk so when
  reading the graph, for example, 8DR5_patch_64j15gtc means an 8 Disk
  RAID5 run against the patch with 64 fio jobs and group-thread_cnt set
  to 16.  'base' in the name is md-next branch as of yesterday.
* Sample fio command: fio --filename=/dev/md0 --direct=1
  --output=/root/remote/8DR5_patch_64j16gtc_1/randrw_131072_1.json
  --rw=randrw --bs=131072 --ioengine=libaio --ramp_time=3 --runtime=60
  --iodepth=1 --numjobs=64 --time_based --group_reporting
  --name=131072_1_randrw --output-format=json --numa_cpu_nodes=0

Results: https://photos.app.goo.gl/Cip1rU3spbD8nvG28 

-Paul