[tracing] Whitelist sync MDP.

[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065
Committed: https://crrev.com/caffce579a5c78540e15a0a280f029abb1781818
Cr-Commit-Position: refs/heads/master@{#435717}

[DmitrySkiba, 2016-11-29 20:18:26]

dskiba@chromium.org changed reviewers:
+ primiano@chromium.org, ssid@chromium.org

[DmitrySkiba, 2016-11-29 20:29:04]

Description was changed from

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms), but
that shouldn't affect usability because the provider runs on SyncThread.

BUG=649065
==========

to

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065
==========

[Primiano Tucci (use gerrit), 2016-11-30 11:36:46]

On 2016/11/29 20:18:27, DmitrySkiba wrote:

Any idea how come 10ms? I glanced through the code and it seems to do very
little. Where does that 10ms come from?
ssid: opinions on the time here? You know all the numbers.

[DmitrySkiba, 2016-11-30 17:55:46]

On 2016/11/30 11:36:46, Primiano Tucci wrote:
> On 2016/11/29 20:18:27, DmitrySkiba wrote:
> 
> Any idea how come 10ms? I glanced through the code and it seems to do very
> little. Where does that 10ms come from?
> ssid: opinions on the time here? You know all the numbers.

That's because EstimateMemoryUsage() neatly hides complexity :) In the end we
end going pretty deep, for example:

Directory::metahandles_map is a std::unordered_map<int64_t,
std::unique_ptr<EntryKernel>>,
EntryKernel::specifics_fields is a EntitySpecificsPtr[PROTO_FIELDS_COUNT],
sync_pb::EntitySpecifics references ~30 other sync_pb fields, which reference
others, etc.

[ssid, 2016-12-01 02:46:23]

On 2016/11/30 17:55:46, DmitrySkiba wrote:
> On 2016/11/30 11:36:46, Primiano Tucci wrote:
> > On 2016/11/29 20:18:27, DmitrySkiba wrote:
> > 
> > Any idea how come 10ms? I glanced through the code and it seems to do very
> > little. Where does that 10ms come from?
> > ssid: opinions on the time here? You know all the numbers.

Currently all the dump providers together typically takes 5-10ms in each
process.
This would probably double this overhead. But, we do not have any other way to
get data about sync usage.

[Primiano Tucci (use gerrit), 2016-12-01 15:45:59]

LGTM as per internal discussion due to the fact that this happens on another
thread, assuming ssid is fine with this.
However, feels like we can do something better / easier for sync. 10 ms of
computation is quite a lot.

[Primiano Tucci (use gerrit), 2016-12-01 15:46:46]

also please keep always +oysteine@ in the loop (read: CC him) when you make
changes to things that affect slow reports.

[DmitrySkiba, 2016-12-01 20:16:57]

The CQ bit was checked by dskiba@chromium.org

[commit-bot: I haz the power, 2016-12-01 20:17:30]

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, 2016-12-01 21:26:20]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1480623417268200, "parent_rev":
"f51dc3850f78a5422d16865cb60668ac5e1ee2bc", "commit_rev":
"4e84f4aeccbf49a0d33ae9d33f533f5178616a80"}

[commit-bot: I haz the power, 2016-12-01 21:26:57]

Description was changed from

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065
==========

to

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065
==========

[commit-bot: I haz the power, 2016-12-01 21:26:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-12-01 21:29:27]

Description was changed from

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065
==========

to

==========
[tracing] Whitelist sync MDP.

Sync MDP takes longer than other whitelisted providers (~10ms on Nexus 5X),
but that shouldn't affect usability because the provider runs on dedicated
thread (SyncThread).

BUG=649065

Committed: https://crrev.com/caffce579a5c78540e15a0a280f029abb1781818
Cr-Commit-Position: refs/heads/master@{#435717}
==========

[commit-bot: I haz the power, 2016-12-01 21:29:28]

Patchset 1 (id:??) landed as
https://crrev.com/caffce579a5c78540e15a0a280f029abb1781818
Cr-Commit-Position: refs/heads/master@{#435717}