Reduce StyleRule class size by eliminating padding in the layout.

Reduce StyleRule class size by eliminating padding in the layout.

This change improves the class size from 40 bytes to 32 byte.
Considering 16-byte allocation granularity on 64-bit Windows this saves
16 bytes per instance (48 bytes to 32 bytes).

When I tested this with cnn.com there were about 7.2K instances of
StyleRule after loading the page (14K instances at the peak).
That means this change will reduce the memory usage by ~112 KB and lower
the peak memory usage by ~219 KB.

Layout before the change:

class blink::StyleRule [sizeof = 40]
  : public blink::StyleRuleBase {
  <padding> (4 bytes)
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
  [sizeof=4] blink::StyleRule::ConsiderForMatching should_consider_for_matching_rules_
  <padding> (4 bytes)
}

Layout after the change:

class blink::StyleRule [sizeof = 32]
  : public blink::StyleRuleBase {
  [sizeof=4] blink::StyleRule::ConsiderForMatching should_consider_for_matching_rules_
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
}

BUG=710933
Review-Url: https://codereview.chromium.org/2833883002
Cr-Commit-Position: refs/heads/master@{#466394}
Committed: https://chromium.googlesource.com/chromium/src/+/3f80504b4bad121fb16e3e7dad008555baf44905

[stanisc, 2017-04-20 20:22:05]

Description was changed from

==========
Reduce StyleRule class size by eliminating padding in the layout.

This change improves the class size from 40 bytes to 32 byte.
Considering 16-byte allocation granularity on 64-bit Windows this saves
16 bytes per instance (48 bytes to 32 bytes).

When I tested this with cnn.com there were about 7.2K instances of
StyleRule after loading the page (14K instances at the peak).
That means this change will reduce the memory usage by ~115 KB and lower
the peak memory usage by 224 KB.

Layout before the change:

class blink::StyleRule [sizeof = 40]
  : public blink::StyleRuleBase {
  <padding> (4 bytes)
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  <padding> (4 bytes)
}

Layout after the change:

class blink::StyleRule [sizeof = 32]
  : public blink::StyleRuleBase {
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
}

BUG=710933
==========

to

==========
Reduce StyleRule class size by eliminating padding in the layout.

This change improves the class size from 40 bytes to 32 byte.
Considering 16-byte allocation granularity on 64-bit Windows this saves
16 bytes per instance (48 bytes to 32 bytes).

When I tested this with cnn.com there were about 7.2K instances of
StyleRule after loading the page (14K instances at the peak).
That means this change will reduce the memory usage by ~112 KB and lower
the peak memory usage by ~219 KB.

Layout before the change:

class blink::StyleRule [sizeof = 40]
  : public blink::StyleRuleBase {
  <padding> (4 bytes)
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  <padding> (4 bytes)
}

Layout after the change:

class blink::StyleRule [sizeof = 32]
  : public blink::StyleRuleBase {
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
}

BUG=710933
==========

[stanisc, 2017-04-20 20:22:49]

stanisc@chromium.org changed reviewers:
+ sky@chromium.org

[stanisc, 2017-04-20 20:22:50]

PTAL!

[stanisc, 2017-04-20 21:07:30]

The CQ bit was checked by stanisc@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-04-20 21:08:21]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[sky, 2017-04-20 21:10:24]

sky@chromium.org changed reviewers:
+ meade@chromium.org
- sky@chromium.org

[sky, 2017-04-20 21:11:14]

While I'm an owner of third_party, you should prefer local owners, especially
for blink changes. I randomly picked meade@ and am removing myself.

[commit-bot: I haz the power, 2017-04-20 22:58:18]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-04-20 22:58:18]

Dry run: This issue passed the CQ dry run.

[meade_UTC10, 2017-04-21 08:27:00]

cool, nice spotting! lgtm

[stanisc, 2017-04-21 18:05:30]

The CQ bit was checked by stanisc@chromium.org

[commit-bot: I haz the power, 2017-04-21 18:06:06]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-21 18:12:32]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1492797930851580, "parent_rev":
"6eedddc3d251b6a6f0aa8ce2612f45c5ecb97c9f", "commit_rev":
"3f80504b4bad121fb16e3e7dad008555baf44905"}

[commit-bot: I haz the power, 2017-04-21 18:12:38]

Description was changed from

==========
Reduce StyleRule class size by eliminating padding in the layout.

This change improves the class size from 40 bytes to 32 byte.
Considering 16-byte allocation granularity on 64-bit Windows this saves
16 bytes per instance (48 bytes to 32 bytes).

When I tested this with cnn.com there were about 7.2K instances of
StyleRule after loading the page (14K instances at the peak).
That means this change will reduce the memory usage by ~112 KB and lower
the peak memory usage by ~219 KB.

Layout before the change:

class blink::StyleRule [sizeof = 40]
  : public blink::StyleRuleBase {
  <padding> (4 bytes)
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  <padding> (4 bytes)
}

Layout after the change:

class blink::StyleRule [sizeof = 32]
  : public blink::StyleRuleBase {
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
}

BUG=710933
==========

to

==========
Reduce StyleRule class size by eliminating padding in the layout.

This change improves the class size from 40 bytes to 32 byte.
Considering 16-byte allocation granularity on 64-bit Windows this saves
16 bytes per instance (48 bytes to 32 bytes).

When I tested this with cnn.com there were about 7.2K instances of
StyleRule after loading the page (14K instances at the peak).
That means this change will reduce the memory usage by ~112 KB and lower
the peak memory usage by ~219 KB.

Layout before the change:

class blink::StyleRule [sizeof = 40]
  : public blink::StyleRuleBase {
  <padding> (4 bytes)
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  <padding> (4 bytes)
}

Layout after the change:

class blink::StyleRule [sizeof = 32]
  : public blink::StyleRuleBase {
  [sizeof=4] blink::StyleRule::ConsiderForMatching
should_consider_for_matching_rules_
  [sizeof=8] blink::CSSSelectorList selector_list_
  [sizeof=8] blink::Member<blink::StylePropertySet> properties_
  [sizeof=8] blink::Member<blink::CSSLazyPropertyParser> lazy_property_parser_
}

BUG=710933

Review-Url: https://codereview.chromium.org/2833883002
Cr-Commit-Position: refs/heads/master@{#466394}
Committed:
https://chromium.googlesource.com/chromium/src/+/3f80504b4bad121fb16e3e7dad00...
==========

[commit-bot: I haz the power, 2017-04-21 18:12:39]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/3f80504b4bad121fb16e3e7dad00...