| jsheeren | hi there | 09:03 |
|---|---|---|
| jsheeren | quick question about running the cloudimages on an openstack platform and specificaly io performance differences between stock xenial and stock trusty with a xenial-lts kernel installed through apt | 09:04 |
| jsheeren | are there differences in the kernel options? | 09:04 |
| jsheeren | the xenial cloud image with kernel 4.4.0-24-generic has almost 2 times better IO performance than the trusty cloud image with the xenial-lts 4.4.0-34-generic kernel | 09:06 |
| jsheeren | which i find surprising as i would expect the same performance | 09:06 |
| mdeslaur | jsheeren: just a theory, but the xenial kernel is built with a newer gcc | 12:56 |
| mdeslaur | 5.4.0 vs 4.8.4 | 12:58 |
| xnox | better/newer userspace too? (depending on how the testing is done....) | 12:58 |
| mdeslaur | that too | 12:58 |
| jsheeren | so the xenial kernel for xenial is built with 5.4.0, the xenial kernel for trusty is built with 4.8.4? | 12:59 |
| mdeslaur | yep | 13:00 |
| xnox | jsheeren, the package for each release is built in the target release build chroot. So all of toolchain for -lts kernels is from the target distro. Everything including things like binutils, glibc, compilers, etc. | 13:01 |
| xnox | the backport kernels are just that -> new source code, new package name, compiled on an old release. | 13:02 |
| jsheeren | just to add hardware compatibility, but not to enhance performance, etc? | 13:02 |
| xnox | it's not a .deb / binary copy. (that would result in naming clash) | 13:02 |
| jsheeren | is it doable to upgrade the gcc on trusty to the version on xenial? or are there too many dependencies that will bork? | 13:03 |
| xnox | jsheeren, there are multiple reasons and multiple usecases as to why hwe kernels were started to be provided. It's a mix of hardware compat / performance / (new)security features | 13:03 |
| xnox | no no no no | 13:03 |
| xnox | that would break the ABI | 13:03 |
| xnox | on c++ | 13:03 |
| jsheeren | ok | 13:03 |
| xnox | i mean kernel is special, cause it's stand-alone / freestanding code. | 13:04 |
| xnox | but we would not do that.... Upgrade to xenial perhaps? =) | 13:04 |
| xnox | it is shiny =) | 13:04 |
| mdeslaur | it's got the "new car" scent | 13:05 |
| jsheeren | xnox: yeah if we run a do-release-upgrade on trusty so we end up with a xenial, the performance issue is the same | 13:06 |
| jsheeren | we've looked at a lot of stuff | 13:06 |
| jsheeren | using the same hypervisor, same openstack flavor, etc | 13:06 |
| jsheeren | a bit stumped at the moment on why we are seeing the IO performance difference that is so large at the moment | 13:06 |
| jsheeren | we compared the sysctl settings as well but did not see any differences that would impact IO | 13:08 |
| xnox | jsheeren, your findings would be interesting. To rule things out, you /could/ *warning not supported* enable xenail repository on trusty, pin it down below trusty with apt-pinning, install/upgrade generic kernel from the xenial repository with e.g. apt install linux-generic/xenial, see what happens. | 13:08 |
| jsheeren | ah yeah, could try that | 13:08 |
| xnox | this way you will rule out if the $userspace in xenial affecting benchmarks, or indeed the 4.4 kernel compiled on xenial, when running trusty userspace, is better. | 13:08 |
| jsheeren | we tried copying the files from a xenial to a trusty but that did not go so well ... heh | 13:08 |
| xnox | yeah.... partial apt upgrade to xenial to get new kernel from xenial rather than via hwe-stack is *safer*. Still a frankenstein =) | 13:09 |
| jsheeren | https://gist.github.com/beci/2a2091f282042ed20cda this is a no go then? | 13:10 |
| === Elimin8r is now known as Elimin8er | ||
| phillw | I take it that the 9134 version is the latest.... Quite a step change from the last one?... | 22:49 |
| phillw | phillw@piglet:~$ ls -lt /boot/abi* | 22:49 |
| phillw | -rw-r--r-- 1 root root 1241623 Aug 16 23:23 /boot/abi-4.4.0-9134-generic | 22:49 |
| phillw | -rw-r--r-- 1 root root 1241623 Jul 27 22:28 /boot/abi-4.4.0-34-generic | 22:49 |
| phillw | Kindest Regards, | 22:49 |
| phillw | Phill. | 22:49 |
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