leveldb: Reuse manifest (AKA logs) during open.

leveldb: Reuse manifest (AKA logs) during open.

All leveldb uses now set the reuse_logs option to trigger a new fast open path.
For db's with prior changes (i.e. non-empty logs) this avoids three fsync calls
(on average) for every open as well as the need to compact (rewrite) the db.

More info at:

https://github.com/google/leveldb/commit/251ebf5dc70129ad3c38193fe6c99a5b0ec6b9fa

BUG=468810
Committed: https://crrev.com/4050991eae26c33acb1c1996fe1900b43ae0fa13
Cr-Commit-Position: refs/heads/master@{#322433}

[cmumford, 2015-03-19 17:45:22]

cmumford@chromium.org changed reviewers:
+ jam@chromium.org, nhiroki@chromium.org

[cmumford, 2015-03-19 17:45:23]

This new setting is already in use by IDB in M41 (all platforms except CrOS).
Another CL will enable it for CrOS. The plan is to monitor corruption rates to
ensure they do not rise before this change goes into stable.

[cmumford, 2015-03-19 18:50:22]

On 2015/03/19 at 17:45:23, cmumford wrote:
> This new setting is already in use by IDB in M41 (all platforms except CrOS).
Another CL will enable it for CrOS. The plan is to monitor corruption rates to
ensure they do not rise before this change goes into stable.

jsbell suggested adding a constant (leveldb_env::kDefaultLogReuseOptionValue) as
we are still validating stability of this new feature on CrOS (see
crrev.com/1023773003), so if CrOS does turn out to be unreliable we will have
only one place to disable log reuse for all leveldb users.

[nhiroki, 2015-03-20 00:20:24]

LGTM for...

- chrome/browser/sync_file_system/
- content/browser/service_worker/
- storage/browser/fileapi/

> For db's with prior changes (i.e. non-empty logs) this avoids three fsync
calls
> (on average) for every open as well as the need to compact (rewrite) the db.

Cool!! :)

[jam, 2015-03-23 16:28:53]

what do you want me to review?

[cmumford, 2015-03-23 16:37:25]

On 2015/03/23 at 16:28:53, jam wrote:
> what do you want me to review?

jam, un-reviewed files are:

chrome/browser/chromeos/drive/resource_metadata_storage.cc
chrome/browser/prefs/leveldb_pref_store.cc
components/leveldb_proto/DEPS
components/leveldb_proto/leveldb_database.cc
content/browser/dom_storage/session_storage_database.cc
content/browser/indexed_db/leveldb/leveldb_database.cc
content/browser/notifications/notification_database.cc
extensions/browser/value_store/leveldb_value_store.cc
google_apis/gcm/engine/gcm_store_impl.cc
sync/internal_api/attachments/on_disk_attachment_store.cc
third_party/leveldatabase/env_chromium.h

[jam, 2015-03-26 15:40:25]

lgtm

https://codereview.chromium.org/1025433003/diff/40001/components/leveldb_prot...
File components/leveldb_proto/DEPS (right):

https://codereview.chromium.org/1025433003/diff/40001/components/leveldb_prot...
components/leveldb_proto/DEPS:2: "+third_party/leveldatabase/src/include",
this isn't needed anymore

[cmumford, 2015-03-26 16:42:00]

The CQ bit was checked by cmumford@chromium.org

[cmumford, 2015-03-26 16:42:01]

The patchset sent to the CQ was uploaded after l-g-t-m from jam@chromium.org,
nhiroki@chromium.org
Link to the patchset: https://codereview.chromium.org/1025433003/#ps60001
(title: "Deleted redundant DEPS path")

[commit-bot: I haz the power, 2015-03-26 16:42:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1025433003/60001

[commit-bot: I haz the power, 2015-03-26 18:28:49]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-03-26 18:29:44]

Patchset 4 (id:??) landed as
https://crrev.com/4050991eae26c33acb1c1996fe1900b43ae0fa13
Cr-Commit-Position: refs/heads/master@{#322433}