DB::Put() to estimate write batch data size needed and pre-allocate buffer

Summary:
In one of CPU profiles, we see some CPU costs of string::reserve() inside Batch.Put(). This patch should be able to reduce some of the costs by allocating sufficient buffer before hand.

Since it is a trivial percentage of CPU costs, I didn't find a way to show the improvement in one of the benchmarks. I'll deploy it to same application and do the same CPU profiling to make sure those CPU costs are reduced.

Test Plan: make all check

Reviewers: haobo, kailiu, igor

Reviewed By: haobo

CC: leveldb, nkg-

Differential Revision: https://reviews.facebook.net/D15135
Pre-calculate whether to slow down for too many level 0 files

Summary: Currently in DBImpl::MakeRoomForWrite(), we do  "versions_->NumLevelFiles(0) >= options_.level0_slowdown_writes_trigger" to check whether the writer thread needs to slow down. However, versions_->NumLevelFiles(0) is slightly more expensive than we expected. By caching the result of the comparison when installing a new version, we can avoid this function call every time.

Test Plan:
make all check
Manually trigger this behavior by applying universal compaction style and make sure inserts are made slow after there are certain number of files.

Reviewers: haobo, kailiu, igor

Reviewed By: kailiu

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D15141
Use sanitized options while opening db

Summary: We use SanitizeOptions() to set appropriate values for some options, based on other options. So we should use the sanitized options by default. Luckily it hasn't caused a bug yet, but can result in a bug in the fugture.

Test Plan: make check

Reviewers: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14103
A script that automatically reformat affected lines

Summary:
Added a script that reformat only the affected lines in a given diff.

I planned to make that file as pre-commit hook but looks it's a little bit more difficult than I thought. Since I don't want to spend too much time on this task right now, I eventually added a "make command" to achieve this with a few additional key strokes.

Also make the clang-format solely inherited from Google's style -- there are still debates on some of the style issues, but we can address them later once we reach a consensus.

Test Plan: Did some ugly format change and ran "make format", all affected lines are formatted as expected.

Reviewers: igor, sdong, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15147
Merge branch 'master' of github.com:facebook/rocksdb into sanitizedOptions
Move the compilation of the shared libraries to "make release"

Compiling the shared libraries took a long time. Thus to speed up the development speed, it still makes sense to be separated from regular compilation.
BuildBatchGroup -- memcpy outside of lock

Summary: When building batch group, don't actually build a new batch since it requires heavy-weight mem copy and malloc. Only store references to the batches and build the batch group without lock held.

Test Plan:
`make check`

I am also planning to run performance tests. The workload that will benefit from this change is readwhilewriting. I will post the results once I have them.

Reviewers: dhruba, haobo, kailiu

Reviewed By: haobo

CC: leveldb, xjin

Differential Revision: https://reviews.facebook.net/D15063
VersionEdit not to take NumLevels()

Summary:
I will submit a sequence of diffs that are preparing master branch for column families. There are a lot of implicit assumptions in the code that are making column family implementation hard. If I make the change only in column family branch, it will make merging back to master impossible.

Most of the diffs will be simple code refactorings, so I hope we can have fast turnaround time. Feel free to grab me in person to discuss any of them.

This diff removes number of level check from VersionEdit. It is used only when VersionEdit is read, not written, but has to be set when it is written. I believe it is a right thing to make VersionEdit dumb and check consistency on the caller side. This will also make it much easier to implement Column Families, since different column families can have different number of levels.

Test Plan: make check

Reviewers: dhruba, haobo, sdong, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15159