[kudu-CR] bootstrap: use the iterator interface to read the log

["Todd Lipcon (Code Review)" <ge...@cloudera.org>]

Hello Adar Dembo, Kudu Jenkins,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/3039

to look at the new patch set (#2).

Change subject: bootstrap: use the iterator interface to read the log
......................................................................

bootstrap: use the iterator interface to read the log

This uses the new log entry reader interface when replaying the log
during tablet bootstrap. Per the previous commit message, this makes
more effective use of allocator and CPU caches, so provides a bit of
a speed-up.

Before:
  Time spent bootstrapping tablet: real 3.825s       user 1.448s     sys 1.000s
  Time spent bootstrapping tablet: real 4.340s       user 1.480s     sys 0.988s
  Time spent bootstrapping tablet: real 7.438s       user 1.456s     sys 1.080s

After:
  Time spent bootstrapping tablet: real 5.563s       user 1.092s     sys 1.172s
  Time spent bootstrapping tablet: real 5.931s       user 1.172s     sys 0.976s
  Time spent bootstrapping tablet: real 8.050s       user 1.188s     sys 1.192s

CPU time is reduced by about a third. In multithreaded bootstrap scenarios,
this is likely to have a more dramatic impact by reducing contention on the
allocator's central free list.

Change-Id: I31075a887d591071386c448d6e8769f92238bb07
---
M src/kudu/tablet/tablet_bootstrap.cc
1 file changed, 32 insertions(+), 32 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/39/3039/2
-- 
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I31075a887d591071386c448d6e8769f92238bb07
Gerrit-PatchSet: 2
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins