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Re: [PATCH gnumach 1/3] kern: improve assert

From: Justus Winter
Subject: Re: [PATCH gnumach 1/3] kern: improve assert
Date: Fri, 19 Dec 2014 11:19:34 +0100
User-agent: alot/0.3.5

Quoting Samuel Thibault (2014-12-19 02:54:17)
> Justus Winter, le Fri 19 Dec 2014 02:48:56 +0100, a écrit :
> > Use the ternary operator to implement `assert' like it is done in the
> > glibc.  The glibcs changelog does not mention the rationale behind
> > this change, but it does improve our IPC performance.
> Mmm, is it not a matter of changing the estimation of probability of
> branching from the compiler?  I guess using an "unlikely" macro would
> get the same benefit in a much more readable and compiler-portable way?

Yes, I tried that first, without getting any improvements.  The libc
once used __builtin_expect for assert too, but stopped (they didn't
mention why in the changelog).

Lacking a specialized IPC microbenchmark I'm using iperf to measure
TCP performance (over netdde), which is greatly influenced by IPC

I'll work a little on my IPC microbenchmark, and try to reproduce my
findings with it.


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