[MPlayer-dev-eng] [PATCH] Use posix_fadvise in stream_file if available

[Tobias Diedrich]

Tobias Diedrich wrote:
> > Playing something from a slow disk/device while also decoding
> > might give something useful (sshfs over wireless maybe?).
> 
> I doubt it, since it does not cause more IO to take place than
> before (vmstat does not show an increased read io rate, the kernel
> checks for already mapped pages) and in the decoding case only a
> miniscule amount of time will be spent on the IO.

FWIW:
~280ms ping, 10000Km between server and client, playing from sshfs.
Server pipe 100Mbit, client pipe FTTH, throughput in this test about
600KB/s
SDTV file this time.
mplayer -noquiet -nosound -benchmark -frames 2000 -vo null

Without patch:
Run1:
BENCHMARKs: VC:   7.286s VO:   0.010s A:   0.000s Sys:  27.134s =
34.429s
BENCHMARK%: VC: 21.1610% VO:  0.0284% A:  0.0000% Sys: 78.8106% =
100.0000%
Run2:
BENCHMARKs: VC:   7.297s VO:   0.010s A:   0.000s Sys:  23.840s =
31.147s
BENCHMARK%: VC: 23.4264% VO:  0.0333% A:  0.0000% Sys: 76.5403% =
100.0000%
Run3:
BENCHMARKs: VC:   7.225s VO:   0.010s A:   0.000s Sys:  24.222s =
31.457s
BENCHMARK%: VC: 22.9691% VO:  0.0322% A:  0.0000% Sys: 76.9987% =
100.0000%
(Sys 76% means really 3% sys and the rest is iowait according to vmstat)

With patch:
Run1:
BENCHMARKs: VC:  10.352s VO:   0.012s A:   0.000s Sys:  85.822s =
96.186s
BENCHMARK%: VC: 10.7624% VO:  0.0126% A:  0.0000% Sys: 89.2250% =
100.0000%
Run2:
BENCHMARKs: VC:  10.093s VO:   0.013s A:   0.000s Sys:  86.267s =
96.374s
BENCHMARK%: VC: 10.4729% VO:  0.0140% A:  0.0000% Sys: 89.5132% =
100.0000%
Run3:
(Sys 89% means really 3% sys and the rest is idle according to vmstat)

Unexpectedly there is a negative impact here in that the used
bandwidth goes down from 600KB/s to 150KB/s.
Interestingly the initial read is fast and then drops to lower
speed.
I'll have to look into that tomorrow...
I'd assume some bad interaction between asynchroniously asking for
those pages and the sshfs implementation...

-- 
Tobias						PGP: http://8ef7ddba.uguu.de