QUIC - Added Net.QuicServerInfo.DiskCacheWaitForDataReadyTime to measure

QUIC - Added Net.QuicServerInfo.DiskCacheWaitForDataReadyTime to measure
actual time QuicStreamFactory state machine was waiting to load QUIC
server information from disk cache.

Retired Net.QuicServerInfo.DiskCacheReadTime.

R=asvitkine@chromium.org, rch@chromium.org

Committed: https://crrev.com/f555077afcbf1e3d6055139f57d69d8dea4a0959
Cr-Commit-Position: refs/heads/master@{#300549}

[Alexei Svitkine (slow), 2014-10-21 14:58:04]

lgtm

[ramant (doing other things), 2014-10-21 15:26:06]

On 2014/10/21 14:58:04, Alexei Svitkine wrote:
> lgtm

Hi Ryan,
  You are right yesterday about loading quic server info from disk taking very
liitle time(awesome memory). The following is the original measurement. During
code reorg, we have included host resolution time also into disk cache read
time.

https://codereview.chromium.org/189963002/diff/10003/net/quic/quic_crypto_cli...

thanks
raman

[Ryan Hamilton, 2014-10-21 18:49:34]

lgtm

Just to be clear, this won't tell us how long it takes to read the data from
disk, simply how much *extra* time it takes beyond the host resolution, right?
Would it make sense to add such a histogram? Perhaps in
disk_cache_based_quic_server_info.cc?

[ramant (doing other things), 2014-10-21 19:10:23]

On 2014/10/21 18:49:34, Ryan Hamilton wrote:
> lgtm
> 
> Just to be clear, this won't tell us how long it takes to read the data from
> disk, simply how much *extra* time it takes beyond the host resolution, right?

right (how much time QUIC state machine is waiting for disk cache to finish).
HostResultion on IO thread and Cache thread reading data from disk are done in
parallel (not sure if it is parallel on mobile or not).

DiskCache.0.AsyncIOTime, DiskCache.0.ReadTime tell how long it takes for cache
thread to do the read from disk.

> Would it make sense to add such a histogram? Perhaps in
> disk_cache_based_quic_server_info.cc?

Good idea. Will add another histogram to disk_cache_based_quic_server_info.cc in
the next CL. That histogram will cover the time it takes to open/create disk
cache entry, reading from disk on cache thread, getting the data back to IO
thread and closing the disk cache entry.

[ramant (doing other things), 2014-10-21 19:10:29]

The CQ bit was checked by rtenneti@chromium.org

[commit-bot: I haz the power, 2014-10-21 19:11:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/667683004/1

[commit-bot: I haz the power, 2014-10-21 20:33:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-21 20:34:12]

Patchset 1 (id:??) landed as
https://crrev.com/f555077afcbf1e3d6055139f57d69d8dea4a0959
Cr-Commit-Position: refs/heads/master@{#300549}