SQL 2016 - It Just Runs Faster - BULK INSERT Uses Vector Instructions (SSE/AVX)
SQL Server 2016 enhanced the bulk insert activities (BULK INSERT), leveraging the CPUs vector instructions. The vector based approach allows the bulk data to be processed faster.
For example, when inserting data from a text file the integer conversion leverages SSE instructions when the character length is more than 4 characters and trace flag 4809 is disabled.
Take the value of '12345678' needing to be converted to the integer value 1,2345,678. A common algorithm used to determine the integer value of each position one might loop over the character array subtracting the value of character '0' from each entry so it can be casted to a BYTE value and shifted to accommodate base 10 mathematics.
Using a single vector instruction, all 8 characters (BYTES) can subtract the '0' character value. The pseudocode looks like this:
vASCIIZero = { '0','0','0','0','0','0','0','0'};
p128Bits = "12345678";
SSE Subtract Instruction(p128Bits, vASCIIZero)
In a single SSE instruction the value is adjusted instead of requiring 8 loops to process the bytes.
'It Just Runs Faster' - SQL Server 2016 takes advantage of CPU vector instructions to improve bulk insert performance.
Suresh Kandoth -Senior SQL Server Escalation Engineer
Bob Dorr - Principal SQL Server Software Engineer
DEMO - It Just Runs Faster: Bulk Insert Character To Integer Conversion
Overview
This demonstration shows the use of vector instructions to perform character string to integer conversions during the BULK INSERT command.
In order to demonstrate the vector instruction capabilities, this demonstration is a narrow reproduction focused on a single vector improvement, not the only vector based improvement. The demonstration highlights ~10% performance increase on a very simple data set.
Steps
- Use SQL Server Management Studio (SSMS) to connect to a SQL Server 2012 or 2014 instance.
- Paste the script below in a new query window and execute (ATL+X) the script to populate demonstration data.
use tempdb
go
create table tblBCP
(
iVal1 bigint NOT NULL,
iVal2 bigint NOT NULL,
iVal3 bigint NOT NULL,
iVal4 bigint NOT NULL,
iVal5 bigint NOT NULL,
iVal6 bigint NOT NULL,
iVal7 bigint NOT NULL,
iVal8 bigint NOT NULL
)
go
set nocount on
go
insert into tblBCP values (12345678, 98765432, 91827364, 54321678, 1234567812345678, 9876543212345678, 9182736412345678, 5432167812345678)
go
insert into tblBCP select * from tblBCP
go 20
From a Windows Command prompt export the demonstration data into a text file.
bcp.exe tempdb..tblBCP out "c:\temp\Ints.bcp" -T -S.\S33 -c -t~
Copy the script below into an SSMS Query Window and execute it, noting the execution outcomes.
create table tblTests
(
iFlag int NOT NULL,
iMSDuration int NOT NULL
)
dbcc traceoff(-1, 4809)
go
dbcc freeproccache
go
declare @iTraceFlag int = 0
declare @iLoops int = 8
while(@iLoops > 0)
begin
set @iLoops = @iLoops -1
truncate table tblBCP
declare @dtStart datetime = GetUTCDate()
BULK INSERT tempdb..tblBCP FROM 'c:\temp\Ints.bcp' WITH (DATAFILETYPE = 'CHAR', FIELDTERMINATOR='~')
insert into tblTests values (@iTraceFlag, DATEDIFF(ms, @dtStart, GetUTCDate()) )
end
go
-- Disable use of SSE
dbcc traceon(-1, 4809)
go
dbcc freeproccache
go
declare @iTraceFlag int = 4809
declare @iLoops int = 8
while(@iLoops > 0)
begin
set @iLoops = @iLoops -1
truncate table tblBCP
declare @dtStart datetime = GetUTCDate()
BULK INSERT tempdb..tblBCP FROM 'c:\temp\Ints.bcp' WITH (DATAFILETYPE = 'CHAR', FIELDTERMINATOR='~')
insert into tblTests values (@iTraceFlag, DATEDIFF(ms, @dtStart, GetUTCDate()) )
end
go
select (([Avg No SSE] / [AvgSSE]) -1.0) * 100.0 as [PERCENT Faster], [Avg No SSE], [AvgSSE]
from
(
select (select avg(iMSDuration) * 1.0 from tblTests where iFlag = 0) as [AvgSSE],
(select avg(iMSDuration) * 1.0 from tblTests where iFlag = 4809) as [Avg No SSE]
) as a
go
Actual Scenarios
SQL Server 2016 has been vetted by a wide range of customers. The positive impact of these changes has been realized by:
- Online retailer can load and respond to competitive price changes faster.
- Credit Card fraud service improved response times from incoming data feed inception to detection.
Sample Results (~10% faster)
Machine |
32GB RAM, 4 Core Hyper-threaded enabled 2.8Ghz, SSD Storage |
SQL Server |
Out of the box, default installation |
SSE Enabled |
3157ms |
SSE Disabled |
3479ms |