On Tue, Feb 27, 2018 at 12:33 PM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 27/02/2018 06:39, Emilio G. Cota wrote:
>> Using a hash table or a binary tree to keep track of the jumps
>> doesn't really pay off, not only due to the increased memory usage,
>> but also because most TBs have only 0 or 1 jumps to them. The maximum
>> number of jumps when booting debian-arm that I measured is 35, but
>> as we can see in the histogram below a TB with that many incoming jumps
>> is extremely rare; the average TB has 0.80 incoming jumps.
>>
>> n_jumps: 379208; avg jumps/tb: 0.801099
>> dist: [0.0,1.0)|▄█▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁ ▁▁▁ ▁▁▁ ▁|[34.0,35.0]
>
> This makes sense, for example:
>
> while(...) {
> }
>
> 2 basic blocks, 0 and 1 incoming jumps (avg 0.5)
>
> if(...) {
> }
>
> 2 basic blocks, 0 and 1 incoming jumps (avg 0.5)
>
> if(...) {
> } else {
> }
>
> 3 basic blocks, 0, 1 and 1 incoming jumps (avg 0.66)
>
> So 0.8 is actually a lot. :) The long tail is probably for switch
> statements.
And calls too :-)
Laurent
> Paolo
>
