On 03/07/2023 05:59, Masahiko Sawada wrote:
On Mon, Jul 3, 2023 at 11:55 AM Masahiko Sawada <sawada.m...@gmail.com> wrote:
After further investigation, the performance degradation comes from
calling posix_fallocate() (called via FileFallocate()) and pwritev()
(called via FileZero) alternatively depending on how many blocks we
extend by. And it happens only on the xfs filesystem.
FYI, the attached simple C program proves the fact that calling
alternatively posix_fallocate() and pwrite() causes slow performance
on posix_fallocate():
$ gcc -o test test.c
$ time ./test test.1 1
total 200000
fallocate 200000
filewrite 0
real 0m1.305s
user 0m0.050s
sys 0m1.255s
$ time ./test test.2 2
total 200000
fallocate 100000
filewrite 100000
real 1m29.222s
user 0m0.139s
sys 0m3.139s
This must be highly dependent on the underlying OS and filesystem. I'm
not seeing that effect on my laptop:
/data$ time /tmp/test test.0 0
total 200000
fallocate 0
filewrite 200000
real 0m1.856s
user 0m0.140s
sys 0m1.688s
/data$ time /tmp/test test.1 1
total 200000
fallocate 200000
filewrite 0
real 0m1.335s
user 0m0.156s
sys 0m1.179s
/data$ time /tmp/test test.2 2
total 200000
fallocate 100000
filewrite 100000
real 0m2.159s
user 0m0.165s
sys 0m1.880s
/data$ uname -a
Linux heikkilaptop 6.0.0-6-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.0.12-1
(2022-12-09) x86_64 GNU/Linux
/data is an nvme drive with ext4 filesystem.
--
Heikki Linnakangas
Neon (https://neon.tech)
