I’m looking for just a few Linode 64 users currently on hosts in the Fremont datacenter (host9 and up) to help test a new performance patch to the host and UML.
UML works by using ptrace, a function of Linux to intercept system calls made by applications. When your UML makes a system call, the host intercepts the call, performs the work inside UML, and null-ifies the system call on the host by converting that system call to “getpid” on the host. The problem with this is that it generates two context switches on the host.
With the [url=http://perso.wanadoo.fr/laurent.vivier/UML/
]sysemu patches[/url] on the host and in UML, it doesn’t bother running “getpid”, thereby reducing number of context switches from 2 to 1.
Here are some “real-world” benchmarks using Mysql’s run-all-tests script:
In short, the tests ran [b]33% faster[/b] than they did without the sysemu patches.
[list][*] We’ll migrate you to host25, keeping your slot on the previous host reserved (in case we need to migrate you back). In case you’ve never migrated before, it’s an automated process which moves your filesystem images to the new host. No changes are required on your end, and downtime is limited to however long it takes to copy your images (usually less than 15 minutes or so for 3GB).
[*] Set your config profile to boot the 2.4.26-linode29-1um kernel
[*] Try to break things[/list]
If things go well for a few days, I’ll consider it stable and open up the server to the public. After another few weeks, we can move the other hosts to this kernel.
Secondly, this will help test 2.6.7-rc1 on the host, an upgrade from the current 2.6.4 kernel.
Thirdly, I would also like for some of you to test the 2.4.26-linode29-1um kernel, to make sure it still functions correctly on hosts without the sysemu patches. Please let me know your experience with this kernel. On non-sysemu enabled hosts, it should perform the same as the previous linode kernels.
Let me know if you’re interested…
Filed under: virtualization by caker