linux-kernel - Re: [PATCH v4] btrfs: zstd: enable negative compression levels mount option

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Message-ID: <20250207194803.GP5777@twin.jikos.cz>
Date: Fri, 7 Feb 2025 20:48:03 +0100
From: David Sterba <dsterba@...e.cz>
To: David Sterba <dsterba@...e.cz>
Cc: Daniel Vacek <neelx@...e.com>, Chris Mason <clm@...com>,
	Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
	Nick Terrell <terrelln@...com>, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] btrfs: zstd: enable negative compression levels mount
 option

On Wed, Feb 05, 2025 at 07:17:05PM +0100, David Sterba wrote:
> On Thu, Jan 30, 2025 at 06:58:19PM +0100, Daniel Vacek wrote:
> > This patch allows using the fast modes (negative compression levels) of zstd
> > as a mount option.
> > 
> > As per the results, the compression ratio is lower:
> > 
> > for level in {-15..-1} 1 2 3; \
> > do printf "level %3d\n" $level; \
> >   mount -o compress=zstd:$level /dev/sdb /mnt/test/; \
> >   grep sdb /proc/mounts; \
> >   cp -r /usr/bin       /mnt/test/; sync; compsize /mnt/test/bin; \
> >   cp -r /usr/share/doc /mnt/test/; sync; compsize /mnt/test/doc; \
> >   cp    enwik9         /mnt/test/; sync; compsize /mnt/test/enwik9; \
> >   cp    linux-6.13.tar /mnt/test/; sync; compsize /mnt/test/linux-6.13.tar; \
> >   rm -r /mnt/test/{bin,doc,enwik9,linux-6.13.tar}; \
> >   umount /mnt/test/; \
> > done |& tee results | \
> > awk '/^level/{print}/^TOTAL/{print$3"\t"$2"  |"}' | paste - - - - -
> > 
> > 		266M	bin  |	45M	doc  |	953M	wiki |	1.4G	source
> > =============================+===============+===============+===============+
> > level -15	180M	67%  |	30M	68%  |	694M	72%  |	598M	40%  |
> > level -14	180M	67%  |	30M	67%  |	683M	71%  |	581M	39%  |
> > level -13	177M	66%  |	29M	66%  |	671M	70%  |	566M	38%  |
> > level -12	174M	65%  |	29M	65%  |	658M	69%  |	548M	37%  |
> > level -11	174M	65%  |	28M	64%  |	645M	67%  |	530M	35%  |
> > level -10	171M	64%  |	28M	62%  |	631M	66%  |	512M	34%  |
> > level  -9	165M	62%  |	27M	61%  |	615M	64%  |	493M	33%  |
> > level  -8	161M	60%  |	27M	59%  |	598M	62%  |	475M	32%  |
> > level  -7	155M	58%  |	26M	58%  |	582M	61%  |	457M	30%  |
> > level  -6	151M	56%  |	25M	56%  |	565M	59%  |	437M	29%  |
> > level  -5	145M	54%  |	24M	55%  |	545M	57%  |	417M	28%  |
> > level  -4	139M	52%  |	23M	52%  |	520M	54%  |	391M	26%  |
> > level  -3	135M	50%  |	22M	50%  |	495M	51%  |	369M	24%  |
> > level  -2	127M	47%  |	22M	48%  |	470M	49%  |	349M	23%  |
> > level  -1	120M	45%  |	21M	47%  |	452M	47%  |	332M	22%  |
> > level   1	110M	41%  |	17M	39%  |	362M	38%  |	290M	19%  |
> > level   2	106M	40%  |	17M	38%  |	349M	36%  |	288M	19%  |
> > level   3	104M	39%  |	16M	37%  |	340M	35%  |	276M	18%  |
> > 
> > Signed-off-by: Daniel Vacek <neelx@...e.com>
> > ---
> > Changes in v4:
> >  * Fix a bug with workspace lru_list.
> >  * Keep the levels down to -15 as agreed.
> 
> Thanks, I'll add the patch to for-next soon. The information about times
> is only a changelog update so this can be done later once we have it.

Now added to for-next.