In Google Chrome/ Chromium net-internals events, what is "DISK_CACHE_ENTRY"?

Question

What are the DISK_CACHE_ENTRY urls in chrome://net-internals/#events, and why are they happening when no remote resources are being asked for?

A google search mostly shows bug reports and source code — is there documentation on this event type available anywhere?

More info:

I am running Chromium Version 43.0.2357.81 Ubuntu 15.04 (64-bit).

The DISK_CACHE_ENTRY urls seem to be coming from my history. For example, I have no remote resources open, but I see this event appear (probably from a past Google Maps visit):

6409    DISK_CACHE_ENTRY    http://maps.gstatic.com/maps-api-v3/api/js/21/4/common.js

To rule out that they are one of the requests in user-configurable Chrome operations, I disabled all extensions, uchecked all options under "Privacy", and disabled all account sync options. I opened only two tabs:

• chrome://net-internals/#events
• http://localhost/ (a simple directory listing with no remote urls)

The events still happen whenever I refresh the localhost tab.

Answer 1

This page may provide some of the documentation you are looking for: https://www.chromium.org/developers/design-documents/network-stack/disk-cache, though it isn't too detailed. Note that they also mention there is an upcoming switch to Disk Cache 3.0 (not sure when exactly).

In terms of the behavior you're seeing, my guess is that you have the setting enabled to allow chrome to preloads data from your history (docs) to speed up the browsing experience, but that's just a guess.