From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Performance issues with /gnu/store in virtual machines
Date: Tue, 22 Aug 2017 16:35:35 +0200
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References: <20170817210547.3fafde57@cbaines.net> <87shgj7vz4.fsf@gnu.org>
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To: Christopher Baines <mail@cbaines.net>
Cc: help-guix@gnu.org

Christopher Baines <mail@cbaines.net> skribis:

> On Tue, 22 Aug 2017 12:11:43 +0200
> ludo@gnu.org (Ludovic Court=C3=A8s) wrote:
>
>> Hi Chris,
>>=20
>> Christopher Baines <mail@cbaines.net> skribis:
>>=20
>> >   1.13    0.000019           0      3853           openat=20=20
>>=20
>> [...]
>>=20
>> >  13.56    0.193014          50      3853           openat=20=20
>>=20
>> So openat(2) is 4 orders of magnitude slower in the VM, which is a
>> problem.
>>=20
>> I guess a large part of that is due to the fact that VM created with
>> =E2=80=98guix system vm=E2=80=99 use unionfs as their root file system, =
which is a
>> FUSE thing (see the =E2=80=9Cvolatile=E2=80=9D options in (gnu system vm=
), (gnu system
>> linux-initrd), and (gnu build linux-boot).)  I=E2=80=99m not sure how we=
 could
>> avoid it.
>
> I'm unsure if the unionfs will be involved though, as find is searching
> in the /gnu/store directory, which is shared with the host:
>
>   TAG_gnu_store on /gnu/store type 9p (ro,relatime,sync,dirsync,trans=3Dv=
irtio)
>
> This might be misunderstanding how mounts work, but this could be
> either layered on top, or below the unionfs, and I'm guessing its on
> top, which in my mind would mean that the unionfs isn't involved?

Oh you=E2=80=99re probably right.  It might be that 9p over virtio is this =
slow.
We should look at what others are doing, I guess it=E2=80=99s a fairly comm=
on
use case.

Ludo=E2=80=99.