[DTrace-devel] [PATCH 3/7] htab: add dt_htab_insert_unique

[Eugene Loh]

On 10/13/21 8:19 AM, Nick Alcock wrote:

> Kris thinks I should just drop this entire commit since it's unused 
> anywhere. I don't think he's wrong.
Yup.  I can for sure live with that.  Still, I have that question about 
the pre-existing code (for my personal education, I suppose):
>> Also, though this is "unrelated" to the patch, I was wondering if you
>> could explain the pre-existing code.  We enter the insert function.  We
>> look for a match.  If none, we'll add a bucket and therefore check the
>> htab size.  If needed, we resize the htab.  At that point, we "retry."
>> Why?  If we failed to find a bucket the first time, why should we find
>> one now?  Or, are we rerunning the search merely for the side effect of
>> recomputing idx?
> The latter :) it avoids having to write the bucket search loop twice.
> We're retrying the bucket search.
I still don't understand.  If the bucket search fails the first time, 
don't we already know it will fail again after the resizing? The only 
side effect I see is the recomputation of idx, which is more easily done 
by replacing "goto retry" with "idx = hval & htab->mask".