Re: [f2fs-dev] [PATCH] f2fs: change virtual mapping way for compression pages

[Daeho Jeong]

Actually, as you can see, I use the whole zero data blocks in the test file.
It can maximize the effect of changing virtual mapping.
When I use normal files which can be compressed about 70% from the
original file,
The vm_map_ram() version is about 2x faster than vmap() version.

2020년 8월 11일 (화) 오후 4:55, Chao Yu <yuchao0@xxxxxxxxxx>님이 작성:
>
> On 2020/8/11 15:15, Gao Xiang wrote:
> > On Tue, Aug 11, 2020 at 12:37:53PM +0900, Daeho Jeong wrote:
> >> From: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >>
> >> By profiling f2fs compression works, I've found vmap() callings are
> >> bottlenecks of f2fs decompression path. Changing these with
> >> vm_map_ram(), we can enhance f2fs decompression speed pretty much.
> >>
> >> [Verification]
> >> dd if=/dev/zero of=dummy bs=1m count=1000
> >> echo 3 > /proc/sys/vm/drop_caches
> >> dd if=dummy of=/dev/zero bs=512k
> >>
> >> - w/o compression -
> >> 1048576000 bytes (0.9 G) copied, 1.999384 s, 500 M/s
> >> 1048576000 bytes (0.9 G) copied, 2.035988 s, 491 M/s
> >> 1048576000 bytes (0.9 G) copied, 2.039457 s, 490 M/s
> >>
> >> - before patch -
> >> 1048576000 bytes (0.9 G) copied, 9.146217 s, 109 M/s
> >> 1048576000 bytes (0.9 G) copied, 9.997542 s, 100 M/s
> >> 1048576000 bytes (0.9 G) copied, 10.109727 s, 99 M/s
> >>
> >> - after patch -
> >> 1048576000 bytes (0.9 G) copied, 2.253441 s, 444 M/s
> >> 1048576000 bytes (0.9 G) copied, 2.739764 s, 365 M/s
> >> 1048576000 bytes (0.9 G) copied, 2.185649 s, 458 M/s
> >
> > Indeed, vmap() approach has some impact on the whole
> > workflow. But I don't think the gap is such significant,
> > maybe it relates to unlocked cpufreq (and big little
> > core difference if it's on some arm64 board).
>
> Agreed,
>
> I guess there should be other reason causing the large performance
> gap, scheduling, frequency, or something else.
>
> >
> >
> >
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> > .
> >