INADA Naoki 1b61a97811 database/sql: reduce lock contention in Stmt.connStmt ... Previouslly, Stmt.connStmt calls DB.connIfFree on each Stmt.css. Since Stmt.connStmt locks Stmt.mu, a concurrent use of Stmt causes lock contention on Stmt.mu. Additionally, DB.connIfFree locks DB.mu which is shared by DB.addDep and DB.removeDep. This change removes DB.connIfFree and makes use of a first unused connection in idle connection pool to reduce lock contention without making it complicated. Fixes #9484 On EC2 c3.8xlarge (E5-2680 v2 @ 2.80GHz * 32 vCPU): benchmark old ns/op new ns/op delta BenchmarkManyConcurrentQuery-8 40249 34721 -13.73% BenchmarkManyConcurrentQuery-16 45610 40176 -11.91% BenchmarkManyConcurrentQuery-32 109831 43179 -60.69% benchmark old allocs new allocs delta BenchmarkManyConcurrentQuery-8 25 25 +0.00% BenchmarkManyConcurrentQuery-16 25 25 +0.00% BenchmarkManyConcurrentQuery-32 25 25 +0.00% benchmark old bytes new bytes delta BenchmarkManyConcurrentQuery-8 3980 3969 -0.28% BenchmarkManyConcurrentQuery-16 3980 3982 +0.05% BenchmarkManyConcurrentQuery-32 3993 3990 -0.08% Change-Id: Ic96296922c465bac38a260018c58324dae1531d9 Reviewed-on: https://go-review.googlesource.com/2207 Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>		2015-01-24 09:56:25 +00:00
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driver
convert_test.go
convert.go
doc.txt
example_test.go
fakedb_test.go	database/sql: make TestDrivers not crash on second run	2014-10-31 09:49:42 -07:00
sql_test.go	database/sql: reduce lock contention in Stmt.connStmt	2015-01-24 09:56:25 +00:00
sql.go	database/sql: reduce lock contention in Stmt.connStmt	2015-01-24 09:56:25 +00:00