SQLOS Task Origins

Ewald Cress explains how SQLOS tasks come into being:

The above system tasks wear their purpose on their sleeves, because the function pointer in the SOS_Task::Param is, well, to the point. The tasks that run user queries are more abstract, because the I/O completion port listener can’t be bothered with understanding much beyond the rudiments of reading network packets – it certainly can’t be mucking about with fluent TDS skills, SQL parsing and compilation, or permission checks.

So what it does is to enqueue a task that speaks TDS well, pointing it to a bunch of bytes, and sending it on its way. Here is an example of such a dispatch, which shows the “input” side of the WorkDispatcher:

Read the whole thing.

Related Posts

Understanding Hash Match Aggregates

Itzik Ben-Gan continues his series on grouping and aggregating data by looking at the hash match aggregation process: The estimated CPU cost for the Hash Aggregate in the plan for Query 8 is 0.166344, and in Query 9 is 0.16903. It could be an interesting exercise to try and figure out exactly in what way […]

Read More

Row Width And Snapshot Isolation

Kendra Little shows us the impact that row width has on snapshot isolation: So I went to work to demonstrate row width impact on the version store — when only a tiny bit column is changed in the row. Here’s how I did the test: I created two tables, dbo.Narrow and dbo.Wide. They each each have a […]

Read More

Categories

July 2017
MTWTFSS
« Jun Aug »
 12
3456789
10111213141516
17181920212223
24252627282930
31