OpenBSD Journal

Bob Beck: t2k13 report - buffer cache improvements

Contributed by weerd on from the flipping-and-tossing dept.

Next up in the t2k13 reports is Bob Beck (beck@). Bob has been with the project for a very long time, with lots of deep knowledge on the buffer cache, an area he worked on during this hackahton:

Well, I'm now back from the t2k13 hackathon in Toronto.

Interestingly, the only commit I actually made during the hackathon was to ports - something I rarely do - but I took a few minutes and extended the torture test suite to include a parallel core dumper Theo and I have been using extensively to abuse uvm, the scheduler and the IO midlayer.

Having said that most of the value I got from the hackathon was time to work with krw@ stabilizing the last bits of bugs in the amd64 buffer flipper diff (currently posted to tech@) which I now expect to go in once the tree stabilizes after the hackathon. I also had some really good discussions with tedu@ and guenther@ about several aspects of things, including the possibility of using the midlayer to add support for devices like sd cards that support trim along with an optimization to support tossing buffers we know the filesystem is no longer ineterested in - Something I am looking at as we speak in another window.... So hopefully users can see some payoff from this soon.

I also spent some time looking at providing some hooks for the nascent hibernation support to talk to the IO midlayer - and to throw away the contents of all caches before hibernating. This will be more stuff I look at in the next week or two as I return home and have closer proximity to my test machines that can support this.

So all in all, for me I was pretty happy - it was a hackathon to finish something and to start something.

Overall the location and productive time for me was great. Many many thanks to John di Marco and everyone at the University of Toronto for providing us with a great facility to work in. A special thanks to my fellow OpenBSD Foundation Director Ken Westerback (krw@) for being the local boots on the ground that organized everything - having done this myself for many years I'm pretty sure he'll need a good rest afterwards. As others have mentioned, local OpenBSD user Russell Sutherland "volunteered" his family to host the developer "BBQ" at the start of the event which was simply outstanding. The food and local Ontario microbrews we were served certainly raised the bar compared to some of the things we've done in the past.

Thanks for your report Bob!

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