GN: Pass a better -j option when using goma

GN: Pass a better -j option when using goma

When using goma, we can pass a big -j to ninja.

R=asiva@google.com, floitsch@google.com, whesse@google.com

Committed: https://github.com/dart-lang/sdk/commit/9c77f4af2f94c0fe0f5a34cb3a1de09a36bb7a63

[zra, 2016-12-08 20:45:51]

zra@google.com changed reviewers:
+ asiva@google.com, whesse@google.com

[zra, 2016-12-08 20:45:52]

@floitsch Would you mind patching this in to see if your build is still slower
than expected? Thanks!

[floitsch, 2016-12-08 22:26:54]

floitsch@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2016-12-08 22:26:55]

Results look good to me.

Before the patch:

$ time ./tools/build.py --gn -m release -a x64 create_sdk
ninja -C out/ReleaseX64 create_sdk
ninja: Entering directory `out/ReleaseX64'
[1946/1946] STAMP obj/create_sdk.stamp

real    5m2.479s
user    2m13.379s
sys     0m16.885s

---

After the patch (and with *much* more local CPU usage):

$ time ./tools/build.py --gn -m release -a x64 create_sdk
ninja -C out/ReleaseX64 create_sdk
ninja: Entering directory `out/ReleaseX64'
[1946/1946] STAMP obj/create_sdk.stamp

real    2m20.539s
user    33m32.993s
sys     1m37.762s

---

Using Goma with -j200:

$ time ninja -j200 -C out/ReleaseX64/ create_sdk
ninja: Entering directory `out/ReleaseX64/'
[1946/1946] STAMP obj/create_sdk.stamp

real    1m28.568s
user    2m16.046s
sys     0m17.955s

[zra, 2016-12-09 17:35:31]

Description was changed from

==========
GN: Default goma to off if there are lots of local CPUs.

Folks that still want Goma can still run gn.py --goma to get it.
==========

to

==========
GN: Pass a better -j option when using goma

When using goma, we can pass a big -j to ninja.
==========

[zra, 2016-12-09 17:36:21]

On 2016/12/08 22:26:55, floitsch wrote:
> Results look good to me.
> 
> Before the patch:
> 
> $ time ./tools/build.py --gn -m release -a x64 create_sdk
> ninja -C out/ReleaseX64 create_sdk
> ninja: Entering directory `out/ReleaseX64'
> [1946/1946] STAMP obj/create_sdk.stamp
> 
> real    5m2.479s
> user    2m13.379s
> sys     0m16.885s
> 
> ---
> 
> After the patch (and with *much* more local CPU usage):
> 
> $ time ./tools/build.py --gn -m release -a x64 create_sdk
> ninja -C out/ReleaseX64 create_sdk
> ninja: Entering directory `out/ReleaseX64'
> [1946/1946] STAMP obj/create_sdk.stamp
> 
> real    2m20.539s
> user    33m32.993s
> sys     1m37.762s
> 
> ---
> 
> Using Goma with -j200:
> 
> $ time ninja -j200 -C out/ReleaseX64/ create_sdk
> ninja: Entering directory `out/ReleaseX64/'
> [1946/1946] STAMP obj/create_sdk.stamp
> 
> real    1m28.568s
> user    2m16.046s
> sys     0m17.955s

Okay. It looks like the real problem was that we weren't passing a nice big -j
to ninja when using goma.

I've backed out the other part of this change, and kept the part of this change
that does that.

PTAL.

[floitsch, 2016-12-09 18:16:11]

LGTM. (but I would wait for an ok from the others).

[Bill Hesse, 2016-12-09 22:11:49]

lgtm

[siva, 2016-12-10 01:25:07]

lgtm

[zra, 2016-12-10 06:11:59]

Description was changed from

==========
GN: Pass a better -j option when using goma

When using goma, we can pass a big -j to ninja.
==========

to

==========
GN: Pass a better -j option when using goma

When using goma, we can pass a big -j to ninja.

R=asiva@google.com, floitsch@google.com, whesse@google.com

Committed:
https://github.com/dart-lang/sdk/commit/9c77f4af2f94c0fe0f5a34cb3a1de09a36bb7a63
==========

[zra, 2016-12-10 06:12:00]

Committed patchset #2 (id:20001) manually as
9c77f4af2f94c0fe0f5a34cb3a1de09a36bb7a63 (presubmit successful).