Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200811033753.783276-1-daeho43@gmail.com> <20200811071552.GA8365@xiangao.remote.csb>
 <3059d7b0-cf50-4315-e5a9-8d9c00965a7c@huawei.com> <CACOAw_yic7GF3E1zEvZ=Gea3XW4fMYdg-cNuu4wfg+uTKMcJqA@mail.gmail.com>
In-Reply-To: <CACOAw_yic7GF3E1zEvZ=Gea3XW4fMYdg-cNuu4wfg+uTKMcJqA@mail.gmail.com>
From:   Daeho Jeong <daeho43@gmail.com>
Date:   Tue, 11 Aug 2020 18:33:26 +0900
Message-ID: <CACOAw_wi3C0iyTVYc3075d4K27NT7BGMGzsKFDDozf=98vWMcA@mail.gmail.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: change virtual mapping way for
 compression pages
To:     Chao Yu <yuchao0@huawei.com>
Cc:     Gao Xiang <hsiangkao@redhat.com>,
        Daeho Jeong <daehojeong@google.com>, kernel-team@android.com,
        linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Plus, when we use vmap(), vmap() normally executes in a short time
like vm_map_ram().
But, sometimes, it has a very long delay.

2020=EB=85=84 8=EC=9B=94 11=EC=9D=BC (=ED=99=94) =EC=98=A4=ED=9B=84 6:28, D=
aeho Jeong <daeho43@gmail.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> Actually, as you can see, I use the whole zero data blocks in the test fi=
le.
> 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.
>
> 2020=EB=85=84 8=EC=9B=94 11=EC=9D=BC (=ED=99=94) =EC=98=A4=ED=9B=84 4:55,=
 Chao Yu <yuchao0@huawei.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
> >
> > 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@google.com>
> > >>
> > >> 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=3D/dev/zero of=3Ddummy bs=3D1m count=3D1000
> > >> echo 3 > /proc/sys/vm/drop_caches
> > >> dd if=3Ddummy of=3D/dev/zero bs=3D512k
> > >>
> > >> - 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.
> >
> > >
> > >
> > >
> > > _______________________________________________
> > > Linux-f2fs-devel mailing list
> > > Linux-f2fs-devel@lists.sourceforge.net
> > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> > > .
> > >