linux-kernel - Re: Variant symlink filesystem

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Message-ID: <56E32C51.80007@nod.at>
Date:	Fri, 11 Mar 2016 21:36:33 +0100
From:	Richard Weinberger <richard@....at>
To:	Cole <cole@...eqint.net>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Variant symlink filesystem

Hi!

Am 11.03.2016 um 21:32 schrieb Cole:
> On 11 March 2016 at 22:24, Richard Weinberger <richard@....at> wrote:
>> Am 11.03.2016 um 21:22 schrieb Cole:
>>> If I remember correctly, when we were testing the fuse version, we hard coded
>>> the path to see if that solved the problem, and the difference between
>>> the env lookup
>>> code and the hard coded path was almost the same, but substantially slower than
>>> the native file system.
>>
>> And where exactly as the performance problem?
>>
>> Anyway, if you submit your filesystem also provide a decent use case for it. :-)
> 
> Thank you, I will do so. One example as a use case could be to allow
> for multiple
> package repositories to exist on a single computer, all in different
> locations, but with
> a fixed path so as not to break the package manager, the correct
> repository then is
> selected based on ENV variable. That way each user could have their own packages
> installed that would be separate from the system packages, and no
> collisions would
> occur.
> 
> If you don't mind me asking, are fuse based file systems meant to be as fast or
> almost as fast as native or in-kernel filesystems? My last experience
> with them was
> that they were substantially slower. I also believe with our version
> of the fuse filesytem
> that we wrote, the env variable was only being looked up during mount, and then
> remained static from there onwards. Do you believe that we should have
> been able to
> achieve performance almost as good as the in-kernel filesystems?

FUSE filesystems are slower.
But IMHO your use case cries for FUSE and it does not seem to be very performance critical
as all you do is managing a symlink farm and redirecting.
IOW all file io can go through the native filesystem.

Thanks,
//richard