[Bug 258204] Extremely poor performance copying directory with lot small files on nvme

From: <bugzilla-noreply_at_freebsd.org>
Date: Wed, 01 Sep 2021 21:17:06 UTC 
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258204

            Bug ID: 258204
           Summary: Extremely poor performance copying directory with lot
                    small files on nvme
           Product: Base System
           Version: 13.0-STABLE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: ali.abdallah@suse.com

Copying over a folder with lot of small files takes a lot of time

time cp -r /usr/src/sys /home/ali/sys
173.58 real         0.00 user         0.90 sys

/dev/gpt/freebsd-root    /        ufs     rw,noatime 2    2
/dev/gpt/freebsd-boot    /bootfs  ufs     rw         1    1
/dev/gpt/freebsd-swap    none     swap    sw         0    0 

/usr/src/sys contains ~500M of data. 

The problematic system is a T495 with nvme device. On the same machine, I
tested copying the same amount of data on OpenSUSE 15.3 with xfs root
partition, and it takes around 1.5 seconds. 

While copying, I see that the 'cp' command spends a lot of time on biord/biowr.

I did a test copying a single large file of 500M, and it impressively fast. 

Please let me know if you need more data.

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