Zack's Kernel News
Zack's Kernel News
Zack Brown reports on improving a hashing function, constant values adjustable at boot time, and dealing with an Intel design flaw.
Improving a Hashing Function
Amir Goldstein posted a small fix to a kernel function that would produce a unique hash value for an input string. He noticed that for 64-bit values, some bits were lost before calculating the hash – resulting in a slightly less good hash. For 32-bit values, he said, no bits were lost, and the code was left unchanged, but since the relevant stringhash.h file had no official maintainer, and Linus Torvalds had done some work on it in the past, Amir asked Linus what he thought of the fix and for advice on how to test it. As Amir put it, "I wouldn't even know where to begin testing its affects, or how to prove if there really is a problem."
Linus dug back into his memory, saying he believed the lost bits were intentional, though he acknowledged, "it's a long time ago, and we've changed some of the hashing since."
But Linus also said, "you're wrong that it's a no-op on 32-bit. It's a very expensive and pointless multiplication there too, even if the shift ends up being a no-op. The name hashing is pretty performance-sensitive."
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
openSUSE Joins End of 10
openSUSE has decided to not only join the End of 10 movement but it also will no longer support the Deepin Desktop Environment.
-
New Version of Flatpak Released
Flatpak 1.16.1 is now available as the latest, stable version with various improvements.
-
IBM Announces Powerhouse Linux Server
IBM has unleashed a seriously powerful Linux server with the LinuxONE Emperor 5.
-
Plasma Ends LTS Releases
The KDE Plasma development team is doing away with the LTS releases for a good reason.
-
Arch Linux Available for Windows Subsystem for Linux
If you've ever wanted to use a rolling release distribution with WSL, now's your chance.
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.