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From: iyzsong@member.fsf.org (=?utf-8?B?5a6L5paH5q2m?=)
Subject: Re: Performance issues with /gnu/store in virtual machines
Date: Tue, 22 Aug 2017 20:51:26 +0800
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References: <20170817210547.3fafde57@cbaines.net> <87shgj7vz4.fsf@gnu.org>
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In-Reply-To: <87shgj7vz4.fsf@gnu.org> ("Ludovic
	\=\?utf-8\?Q\?Court\=C3\=A8s\=22'\?\=
	\=\?utf-8\?Q\?s\?\= message of "Tue, 22 Aug 2017 12:11:43 +0200")
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To: Ludovic =?utf-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Cc: help-guix@gnu.org

ludo@gnu.org (Ludovic Court=C3=A8s) writes:

> Hi Chris,
>
> Christopher Baines <mail@cbaines.net> skribis:
>
>>   1.13    0.000019           0      3853           openat
>
> [...]
>
>>  13.56    0.193014          50      3853           openat
>
> So openat(2) is 4 orders of magnitude slower in the VM, which is a
> problem.
>
> 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, w=
hich is a FUSE
> thing (see the =E2=80=9Cvolatile=E2=80=9D options in (gnu system vm), (gn=
u system
> linux-initrd), and (gnu build linux-boot).)  I=E2=80=99m not sure how we =
could
> avoid it.

We might switch to the linux kernel's bultin overlayfs, which should be
faster.

https://wiki.archlinux.org/index.php/Overlay_filesystem