[serializer] do not copy code if snapshot is not required to be deterministic.

[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org

Committed: https://crrev.com/5a88c04741476fbb97f0adbdb630a9215aad0ca1
Cr-Commit-Position: refs/heads/master@{#36350}

[Yang, 2016-05-19 05:56:00]

Description was changed from

==========
[serializer] do not copy code if no predictable snapshot is expected.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org
==========

to

==========
[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org
==========

[vogelheim, 2016-05-19 06:58:12]

lgtm

Wow, that's >10% only for that copy!!

[Yang, 2016-05-19 07:19:43]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2016-05-19 07:19:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1991033003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1991033003/1

[commit-bot: I haz the power, 2016-05-19 08:15:07]

Description was changed from

==========
[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org
==========

to

==========
[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org
==========

[commit-bot: I haz the power, 2016-05-19 08:15:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-05-19 08:18:08]

Description was changed from

==========
[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org
==========

to

==========
[serializer] do not copy code if snapshot is not required to be deterministic.

Code in V8 embeds memory addresses. Upon deserialization, those addresses will
be updated anyways, so it's not important whether the serializer records those
addresses. In order to have a deterministic build, we create a copy of the code
and null out memory addresses and serialize this copy.

For the code cache, we do not care about determinism. By avoiding the copy we
can save some time spent on serialization. For the mandreel script in Octane,
this reduces the serialization time from ~85ms to ~75ms.

R=vogelheim@chromium.org

Committed: https://crrev.com/5a88c04741476fbb97f0adbdb630a9215aad0ca1
Cr-Commit-Position: refs/heads/master@{#36350}
==========

[commit-bot: I haz the power, 2016-05-19 08:18:10]

Patchset 1 (id:??) landed as
https://crrev.com/5a88c04741476fbb97f0adbdb630a9215aad0ca1
Cr-Commit-Position: refs/heads/master@{#36350}