IEX market data, CreateEvent & CPU spikes

February 23, 2017

This week I’ve been testing the SpreadServe addin with Tiingo’s IEX market data. I was checking performance on my sscalc0.online AWS host for a group of SpreadServeEngines executing various test and demo spreadsheets, including one that subscribes to IEX tickers for AAPL & SPY, via Tiingo API websockets. That API gives us real time top of book as well as last trade price and size for the cash equity traded on IEX. In my test scenario I was running five engines, two of them idle, three running spreadsheets, one of which was a simple IEX market data subscriber. Using Process Explorer I saw some odd CPU spiking on the idle engines. Zooming in with Process Explorer I could see the busyness was on a thread that should have been idle, sleeping inside a WaitForSingleObject call, waiting for a signal to check its input queue. The event object waited upon was created by some generic code invoking win32’s CreateEvent and also used in another thread. Reading the docs I found that CreateEvent’s fourth param, the event object name, implies that the caller will get a handle to a previously created event object if the names match. And I was using a hardwired name! So my thread was being repeatedly woken by events from another thread. A quick fix to make the names unique produced idling engines with no unnecessary CPU burn. All very instructive, partly because running on AWS makes one very aware of paying by the CPU hour.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s