On Mon, Jul 3, 2023 at 4:36 PM Heikki Linnakangas <hlinn...@iki.fi> wrote: > > 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.
Right. The above were the result where I created the file on the xfs filesystem. The kernel version and the xfs filesystem version are: % uname -rms Linux 4.18.0-372.9.1.el8.x86_64 x86_64 % sudo xfs_db -r /dev/nvme4n1p2 xfs_db> version versionnum [0xb4b5+0x18a] = V5,NLINK,DIRV2,ATTR,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK As far as I tested, it happens only on the xfs filesystem (at least the above version) and doesn't happen on ext4 and ext3 filesystems. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com
