[vlc-devel] [PATCH 1/2] access: file: remote FS can't FAST_SEEK

[Alexandre Janniaux]

Hi,

On 2019-04-16 17:39, Rémi Denis-Courmont wrote:
> Le tiistaina 16. huhtikuuta 2019, 14.30.39 EEST Thomas Guillem a écrit 
> :
>> Reminder: FAST_SEEK set to false will trigger remote tweaks like the 
>> stream
>> prefetcher.
> 
> I wrote the prefetcher and I disagree. If you mount a file system, 
> there is a
> reasonable expectation that it works like a local filesystem - meaning 
> that it
> is fast. The prefetch caching is not designed and suited for that case.

I agree that the prefetcher being not designed for that case is a valid 
point
against the patch, but expecting all mounted file system to be fast 
seems
like a big shortcut to me and might be a noticeable flaw in VLC in case 
it's not,
although I don't really know how to set up something else for the most 
general
use case.

Would another cache strategy fit here or is this an UX issue not 
solvable by
autodetection? Using a file explorer to find medias and play them seems 
like
one of the usual way to use VLC, and distributions are probably using 
FUSE in
this case to make it available for every software, which also seems 
reasonable
and probably expected by users.

If I can, could you explain why prefetch is not suited? Is it because of 
cases
for which FUSE fs is not on network? The documentation in prefetch.c 
states
this but I don't know how much it is related to your argument.

```
/* For local files, the operating system is likely to do a better work 
at
      * caching/prefetching. Also, prefetching with this module could 
cause
      * undesirable high load at start-up. Lastly, local files may 
require
      * support for title/seekpoint and meta control requests. */
```


Regards,

--
Alexandre Janniaux