Falcon is not InnoDB
Presented by,
MySQL & O’Reilly Media, Inc.
Kevin Lewis, Falcon Team Lead
Ann Harrison, Falcon Team
[email protected], [email protected]
Falcon is not InnoDB





Different design
Different concurrency methods
Different sweet spots
Different quirks
Different performance
Design differences
 InnoDB is modeled after Oracle
Clustered storage
Old versions stored in log
Mixed MVCC and locking
 Influenced by MySQL
Statement based logging
File per table / index
Table name rules
Design differences
 Falcon derives loosely from Rdb and InterBase
Starkey design
Pure MVCC
Originally had no log – careful write for durability
 Designed for large memory multi-processors
Page cache plus record cache
Finely grained multi-threading
Synchronization (read/write) on shared structures
Concurrency
 Both default to Repeatable Read
 Neither is exactly Repeatable Read per
ISO/SQL
 Differ from each other in implementation
InnoDB mixes MVCC and locking
Falcon is pure MVCC
 Differ from each other in quirks
Different sweet spots
 True of all databases
 If you design an application to make best use of
Database A, moving to Database B will be hard
 The more you know about A, the harder it will
be to move to B
 InnoDB is part of the MySQL family and will be
into the future
Different quirks
 Serializable is serializable
 Everything else is quirky in different ways
 Standard repeatable read
Select returns the same results
Plus any insert that gets committed
Equivalent to pure locking
read locks + write locks w/o predicate locks
 Mix in MVCC and you get write anomalies
Falcon quirk 1
 On two tables
 Insert into t1 (f1) select count (*) from t1M
Falcon quirk 1
 Trans1:
Insert into t1 (f1)
select count (*)
from t1
 Trans2:
Insert into t1 (f1)
select count (*)
from t1
 Repeat
mysql> select * from t1;
+------+
| f1 |
+------+
| 0|
| 0|
| 1|
| 1|
+------+
4 rows in set (0.00 sec)
Falcon quirk 1
 Innodb makes
transaction 2 wait for
transaction 1’s commit,
then stores the “right”
values in the table
 Transaction 2 has an
inconsistent view of data
mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|
0|
+----------+
mysql> insert into t1 (f1) select count(*)
from t1;
mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|
1|
+----------+
mysql> select * from t1;
+------+
| f1 |
+------+
| 2|
+------+
Falcon quirk 2
 Exchange values between two tables using two
transactions
 Neither “sees” the other’s changes
Falcon quirk 2
Transaction1:
mysql> select * from dinner_menu;
mysql> update lunch_menu
+--------+-------+
->
set price =
| entree | price |
->
(select price * 0.5 from
+--------+-------+
->
from dinner_menu where
| steak | 25.00 |
->
dinner_menu.entree =
+--------+-------+
->
lunch_menu.entree);
mysql> select * from lunch_menu;
Transaction 2:
+--------+-------+
mysql> update dinner_menu
| entree | price |
->
set price =
+--------+-------+
->
(select price * 0.5
| steak | 5.00 |
->
from lunch_menu where
+--------+-------+
->
lunch_menu.entree =
->
dinner_menu.entree);
Falcon quirk 2
mysql> select * from lunch_menu;
+--------+-------+
| entree | price |
+--------+-------+
| steak | 12.50 |
+--------+-------+
mysql> select * from dinner_menu;
+--------+-------+
| entree | price |
+--------+-------+
| steak | 10.00 |
+--------+-------+
 InnoDB transaction 2
waits for transaction 1 to
commit, then gets the
“correct” result
InnoDB quirk 1
mysql> select * from t1;
 Select for update sees a
different scope than
normal select
| f1 |
+------+
+------+
|
1|
+------+
mysql> select * from t1 for update;
+------+
 With consistent-read off,
Falcon does the same
| f1 |
+------+
|
5|
+------+
InnoDB quirk 2
 InnoDB does implicit
“select for update” in
some subqueries
mysql> select * from t1;
+------+
| f1 |
+------+
|
1|
+------+
 Falcon does not
mysql> create table t2 as select * from t1;
mysql> select * from t2;
+------+
| f1 |
+------+
|
5|
+------+
Falcon Architecture – short form
Serial
Log
Record cache
Gophers
Back end
Page Cache
I/O Threads
Front end
Tablespace
Files
Performance
 Where we were last year
 Performance peaks were good
 Standard deviation excessive
25000
20000
15000
InnoDB(2008-4-16)
Falcon(2008-2-27)
10000
5000
0
8
16
32
64
128
Performance problem 1
 Problem
Quick benchmarks had bad results
 Symptom
Auto-commit / select * was slow
 Solution
Reuse read-only transactions
Reduce the cost of transaction startup
Non-blocking scavenge
Falcon performance problem 2
 Problem
DBT2 times degraded badly
 Symptom
Running a monitoring task improved performance
 Solution
First, slow down the front end
Put a limit on the number of Active transactions
that can be committed but not “write complete”
Second, speed up the back end
Falcon’s back end
 From Log to Page Cache - Gopher threads
Add a pool (‘herd’) of Gophers threads
 From Page Cache to disk
Add a pool of I/O threads
Direct IO
Page Consolidation
Thread Prioritization
Falcon performance problem 3
 Problem
Index access (read and insert) was disappointing
 Symptom
Significant (>10%) time spent in locating index entry
points
 Solution
Add Supernode lookup to each index page
Compromise between density of prefix compression and
speed of binary search
Falcon performance problem 4
 Problem
Dbt2 tests were disappointing and erratic
 Symptom
Some tests were OK, many weren’t
Standard deviation was large
 Solution
Hold the mutex in sync object to avoid missing a wakeup call between recognizing the need to wait and going
to sleep.
Falcon performance April 2008
 CPU bound performance is better.
 10 warehouse DBT2 (900 Mb)
 16-way, 32GB Intel Caneland, 4 disk RAID 10
25000
20000
15000
Falcon(2008-4-9)
Falcon(2008-2-27)
10000
InnoDB(2008-4-16)
5000
0
8
16
32
64
128
Falcon vs InnoDB - Dec, 2007
18000
16000
14000
12000
10000
INNODB-20080219
FALCON-20071224
8000
6000
4000
2000
0
8
16
32
64
128
192
After Transaction Fix
18000
16000
14000
12000
INNODB-20080219
10000
FALCON-20071224
FALCON-20080215
8000
FALCON-20080219
6000
4000
2000
0
8
16
32
64
128
192
No Thread Stalls !
18000
16000
14000
12000
INNODB-20080219
10000
FALCON-20071224
FALCON-20080215
8000
FALCON-20080219
FALCON-20080326
6000
4000
2000
0
8
16
32
64
128
192
Today
18000
16000
14000
12000
INNODB-20080219
FALCON-20071224
10000
FALCON-20080215
FALCON-20080219
8000
FALCON-20080326
FALCON-20080414
6000
4000
2000
0
8
16
32
64
128
192
Record Cache / Page Cache
 100 Warehouses (9GB) with 2GB Falcon Cache
3500
3000
2500
2000
350M/1650M
700M/1300M
1000M/1000M
1500
1300M/700M
1000
500
0
8
16
32
64
128
Falcon Feature Preview
http://forge.mysql.com/wiki/Falcon_Feature_Preview
 Questions ?