FreeBSD Release Engineer Scott Long on SMP

I highly recommend that FreeBSD enthusiasts read Scott Long's interview at Onlamp.com. He succinctly explains FreeBSD's new Symmetric MultiProcessing Next Generation (SMPng) code and answers good questions posed by interviewer Federico Biancuzzi.


Since I maintain multiple Dell PowerEdge 750 servers with Hyper-Threading Technology (HTT), I found Scott's comments on gains from HTT to be interesting. It seems that HTT will only be useful once the new ULE scheduler is equipped to make use of HTT and ULE replaces the 4BSD scheduler. Scott says:

"The other design goal of ULE was to have it map out and understand the CPU topology and make good scheduling choices for features like Hyper-Threading. Unfortunately, to my knowledge this work is not yet complete.

[Frederic asks:] Does SMPng improve performance on Intel Hyper-Threading capable CPUs?

Scott Long: As of right now, very little. The scheduler really needs to be aware of Hyper-Threading and schedule threads and processes appropriately so that the caches and TLBs [Transaction Look-aside Buffers] can be shared and not get thrashed. The ULE scheduler will fill this role in the future, but it's not there yet."

Scott also discusses how the network stack will benefit from the removal of the GIANT lock, and how the Pf firewall imported from OpenBSD already runs without GIANT, unlike IPFW. This means Pf is believed to be faster on FreeBSD than IPFW.

Comments

Post a Comment

Popular posts from this blog

Zeek in Action Videos

Image
This is a quick note to point blog readers to my Zeek in Action YouTube video series for the Zeek network security monitoring project .  Each video addresses a topic that I think might be of interest to people trying to understand their network using Zeek and adjacent tools and approaches, like Suricata, Wireshark, and so on.  I am especially pleased with Video 6 on monitoring wireless networks . It took me several weeks to research material for this video. I had to buy new hardware and experiment with a Linux distro that I had not used before -- Parrot .  Please like and subscribe, and let me know if there is a topic you think might make a good video.
Read more

MITRE ATT&CK Tactics Are Not Tactics

Image
Just what are "tactics"? Introduction MITRE ATT&CK  is a great resource, but something about it has bothered me since I first heard about it several years ago. It's a minor point, but I wanted to document it in case it confuses anyone else. The MITRE ATT&CK Design and Philosophy document from March 2020 says the following: At a high-level, ATT&CK is a behavioral model that consists of the following core components: • Tactics, denoting short-term, tactical adversary goals during an attack; • Techniques, describing the means by which adversaries achieve tactical goals; • Sub-techniques, describing more specific means by which adversaries achieve tactical goals at a lower level than techniques; and • Documented adversary usage of techniques, their procedures, and other metadata. My concern is with MITRE's definition of "tactics" as "short-term, tactical adversary goals during an attack," which is oddly recursive. The key word in the tacti...
Read more

New Book! The Best of TaoSecurity Blog, Volume 4

Image
  I've completed the TaoSecurity Blog book series . The new book is  The Best of TaoSecurity Blog, Volume 4: Beyond the Blog with Articles, Testimony, and Scholarship .  It's available now for Kindle , and I'm working on the print edition.  I'm running a 50% off promo on Volumes 1-3 on Kindle through midnight 20 April. Take advantage before the prices go back up. I described the new title thus: Go beyond TaoSecurity Blog with this new volume from author Richard Bejtlich. In the first three volumes of the series, Mr. Bejtlich selected and republished the very best entries from 18 years of writing and over 18 million blog views, along with commentaries and additional material.  In this title, Mr. Bejtlich collects material that has not been published elsewhere, including articles that are no longer available or are stored in assorted digital or physical archives. Volume 4 offers early white papers that Mr. Bejtlich wrote as a network defender, either for technica...
Read more