Message-ID: <bb87534811ecd092bbc6d361df9d02aff35b17ed.camel@redhat.com>
Subject: Re: [PATCH v3 0/6] Composefs: an opportunistically sharing verified
 image filesystem
From:   Alexander Larsson <alexl@redhat.com>
To:     Jingbo Xu <jefflexu@linux.alibaba.com>,
        Amir Goldstein <amir73il@gmail.com>
Cc:     Gao Xiang <hsiangkao@linux.alibaba.com>, gscrivan@redhat.com,
        brauner@kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, david@fromorbit.com,
        viro@zeniv.linux.org.uk, Vivek Goyal <vgoyal@redhat.com>,
        Miklos Szeredi <miklos@szeredi.hu>
Date:   Wed, 01 Feb 2023 10:52:44 +0100
In-Reply-To: <ea8819bc-c340-bf4c-ad91-1a520fe3914b@linux.alibaba.com>
References: <cover.1674227308.git.alexl@redhat.com>
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On Wed, 2023-02-01 at 16:59 +0800, Jingbo Xu wrote:
>=20
> I redid the test with suggestion from Amir, with all files inside the
> erofs layer are redirected to the same lower block, e.g.
> "/objects/00/014430a0b489d101c8a103ef829dd258448a13eb48b4d1e9ff0731d1
> e82b92".
>=20
> The result is shown in the fourth line.
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | uncached(ms)| cached(=
ms)
> ----------------------------------|-------------|-----------
> composefs (with digest)=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 | 326=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| 1=
35
> erofs (w/o -T0)=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 264=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| 172
> erofs (w/o -T0) + overlayfs=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 651=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| 238
> erofs (hacked and redirect to one |=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0|
> lower block) + overlayfs=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0 | 400=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| 230
>=20
> It seems that the "lazy lookup" in overlayfs indeed optimizes in this
> situation.
>=20
>=20
> The performance gap in cached situation (especially comparing
> composefs
> and standalone erofs) is still under investigation and I will see if
> there's any hint by perf diff.

The fact that plain erofs is faster than composefs uncached, but slower
cached is very strange. Also, see my other mail where erofs+ovl cached
is slower than squashfs+ovl cached for me. Something seems to be off
with the cached erofs case...


--=20
=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D=
-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-
=3D-=3D-=3D
 Alexander Larsson                                            Red Hat,
Inc=20
       alexl@redhat.com            alexander.larsson@gmail.com=20
He's a sword-wielding alcoholic barbarian She's a pregnant snooty nun
who=20
dreams of becoming Elvis. They fight crime!=20