linuxaudio.org

Dan Muresan wrote:
> > I haven't measured it, but my educated guess is that if you're

quoted text
> > reading 16384 frames at a time from a FLAC file on current hardware,

> > then the difference between reading st_blksize sized blocks and

>

> Uh, actually no. If one reads 4096, 2048, or 1024 frames the result is

> the same -- 4 bytes less than st_blksize -- EVERY syscall. Try it. In

> any case, I didn't optimize anything like that yet. It was a design

> discussion. I was saying that's one more reason why it's good to have

> the VIO layer, since there is no userspace cache.

>

> > non-st_blksize sized blocks will be absolutley swamped, by disk

> > latencies, cache latencies, scheduling latencies and file

> > decoding overhead.

>

> You seem to mix up latency and CPU load? A program can have low

> latency, yet high(er than necessary) CPU load.

I think you missed the point.
The point is that if you set out to measure the difference

(in CPU load or in latency) between reading st_blksize size

blocks and st_blocksize - 4 blocks at the libsndfile API level,

your measurements would be so swamped with noise from other

factors that any differences would be statistically irrelevant.
Erik

--

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Erik de Castro Lopo

http://www.mega-nerd.com/

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