Re: [f2fs-dev] [PATCH 1/3] f2fs-tools: give less overprovisioning space

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 10/21, Shinichiro Kawasaki wrote:
> On Oct 20, 2022 / 16:18, Jaegeuk Kim wrote:
> 
> ...
> 
> > Thanks, I think that fix looks good to me. I applied into the original patch.
> > https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git/commit/?h=dev&id=281d3e72370f6c39c0d57acaf37a7f0e003ddd28
> 
> Oh, happy to know that the fix is good. And thank you for adding my SoB tag.
> 
> One more thing, my fix missed care for fsck/resize.c. I suggest to apply one
> more hunk below to the commit in same manner as mkfs/f2fs_format.c.
> 
> diff --git a/fsck/resize.c b/fsck/resize.c
> index c048b16..79945e1 100644
> --- a/fsck/resize.c
> +++ b/fsck/resize.c
> @@ -476,8 +476,8 @@ static void rebuild_checkpoint(struct f2fs_sb_info *sbi,
>                         get_cp(rsvd_segment_count)) *
>                         c.new_overprovision / 100);
> 
> -       if (get_cp(rsvd_segment_count) > get_cp(overprov_segment_count))
> -               ASSERT_MSG("Cannot support wrong overprovision ratio\n");
> +       if (get_cp(overprov_segment_count) < get_cp(rsvd_segment_count))
> +               set_cp(overprov_segment_count, get_cp(rsvd_segment_count));
> 
>         DBG(0, "Info: Overprovision ratio = %.3lf%%\n", c.new_overprovision);
>         DBG(0, "Info: Overprovision segments = %u (GC reserved = %u)\n",
> 
> Without this change, the assert message "Cannot support wrong overprovision
> ratio" was printed when I ran resize.f2fs -t X command to the f2fs formatted
> with mkfs.f2fs -s Y. With the change above, the assert message is not printed.

Thanks, applied.

> 
> > 
> > > 
> > > FYI, I tried to fix and created a patch which allows reserved segments larger
> > > than overprovisioning segments [1]. It compares those two, and take larger one
> > > to subtract from usable segments to get the segments for users. I confirmed it
> > > keeps small number of overprovisioning segments for no -s option case, and
> > > avoids the mkfs.f2fs failure for the -s option and zoned block device cases.
> > > However, it increases runtime of my test script which fills f2fs and do file
> > > overwrites to test f2fs GC on zoned block devices. It takes +60% longer runtime.
> > > Then GC performance looks worse than before, and this fix does not look good
> > > for me.
> > 
> > I think you can try to avoid that by tuning /sys/fs/f2fs/xx/reserved_blocks?
> 
> Thanks, I was able to shorten the runtime using the sysfs attribute. So the
> longer GC time was just caused by the smaller reserved segments size. Good.
> 
> -- 
> Shin'ichiro Kawasaki


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