[BUGFIX beta] Set models array length in link-to.

[nathanhammond]

We know the array length in advance so we should set it.

Proof:
http://jsperf.com/array-push-new-literal

[stefanpenner]

LGTM

[rwjblue]

This seems to be throwing an error when params is empty.

[stefanpenner]

if params are empty, we may want to skip allocating and later traversing at all.

[rwjblue]

ya, agreed

[rwjblue]

Once that last issue is fixed, can you prefix with [BUGFIX beta]? Seems pretty safe to pull down into beta, and we'll take all the perfs we can get!

[stefanpenner]

It would be nice if provided perfs had demonstrable improvements in ember. An example or benchmark illustrating this improvement would be nice.

[krisselden]

@stefanpenner agreed, often micro benchmarks like this have no noticeable impact on a macro benchmark due to the improved code being a small percentage of the macro case. I'm fine with merging but am curious if this has any impact on a benchmark of list with link-to components.

[nathanhammond]

In emberperf it is about 2% faster across multiple runs, presumably by just pulling it out into a function which can be optimized separately, but that doesn't exercise the models use case where we should actually get our performance win.

Tests pass now, tagged correctly.

Ember Version: link-to modifications

.---------------------------------------------------------------.
|               Ember Performance Suite - Results               |
|---------------------------------------------------------------|
|           Name           | Speed  | Error  | Samples |  Mean  |
|--------------------------|--------|--------|---------|--------|
| Render List with link-to |   7.23 | 403.89 |      91 | 138.26 |
| Render link-to           | 379.13 |   5.93 |    1010 |   2.64 |
'---------------------------------------------------------------'

Ember Version: Canary

.---------------------------------------------------------------.
|               Ember Performance Suite - Results               |
|---------------------------------------------------------------|
|           Name           | Speed  | Error  | Samples |  Mean  |
|--------------------------|--------|--------|---------|--------|
| Render List with link-to |   6.87 | 528.64 |      86 | 145.51 |
| Render link-to           | 371.58 |   4.84 |    1004 |   2.69 |
'---------------------------------------------------------------'

[mixonic]

Thanks @nathanhammond :-)