strace scheduling fairness

Dmitry V. Levin ldv at
Thu May 17 18:01:53 UTC 2012

On Wed, May 16, 2012 at 12:47:14PM +0200, Denys Vlasenko wrote:
> On 05/16/2012 11:48 AM, Dmitry V. Levin wrote:
> >> One solution is to run waitpid() in a loop until it returns 0 "no more tracees
> >> to wait", then handle them all. It was NAKed a few years ago.
> >
> > It would be nice to have a look at that discussion.  Do you have a
> > reference?  What was the rationale that time?
> I guess Roland saw it as "ugly" and "trying to work around ptrace API
> which is a hopelessly bad API anyway".
> On the technical note, it adds additional waitpid call per every
> syscall entry/exit,

So its cost is quite noticeable, and therefore this fair scheduling is not
always desirable.  Is it possible to implement the feature as an option?

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