Re: [patch] Latency Tracer, voluntary-preempt-2.6.8-rc4-O6

Ingo Molnar
2004-08-17T07:47:50Z

* Lee Revell <rlrevell@joe-job.com> wrote:

> I have attached a patch that effectively disables extract_entropy. I
> am adding Theodore T'so to the cc: list as he is the author of the
> code in question.
>
> For the time being this hack is required to avoid ~0.5 ms
> non-preemptible sections caused by the excessive memcpy's in
> extract_entropy.

i'm not 100% sure it's the memcpy's - but it's extract_entropy()
overhead. Might be the algorithmic slowness of SHATransform().

> + return nbytes;
> +

since this effectively disables the random driver i cannot add it to the
patch.

there's another thing you could try: various SHA_CODE_SIZE values in
drivers/char/random.c. Could you try 1, 2 and 3, does it change the
overhead as seen in the trace?

Ingo