Link time optimizations are also at least turned on in other distros like Fedora, OpenSuse (two years) and Ubuntu (one year).
...
The proposal is to turn on LTO by default on most 64bit release architectures.
...
...
Link time
optimizations are also at least turned on in other distros like Fedora, OpenSuse (two years) and Ubuntu (one year).
...
The idea is to file wishlist bug reports for those 373 packages and then see how far we get, and if it's feasible to already turn on LTO for bookworm.
If not, it should be turned on by default for the following release.
Matthias
On Fri, Jun 17, 2022 at 10:18:43AM +0200, Matthias Klose wrote:
The proposal is to turn on LTO by default on most 64bit release architectures.
By what factor does -ffat-lto-objects increase disk space usage during package builds?
Please coordinate with DSA to ensure that the buildds on these
architectures have sufficient diskspace.
amd64 buildds have/had(?) only 74 GB of diskspace, which has even
without LTO already forced some packages to do manual cleanup steps
during the build to stay within the limited disk space.
A bigger worry is the schedule of such a change.
A major toolchain change shortly before the freeze means the vast
majority of packages will be shipped with non-LTO builds in the release,
LTO significantly increase memory requirements for buildd machines. Do we have
enough RAM and swap on each build server?
Link time optimizations are also at least turned on in other distros like Fedora, OpenSuse (two years) and Ubuntu (one year).
I know Ubuntu has builders with 8 GB RAM + 4 GB swap which is not enough in all cases. https://answers.launchpad.net/launchpad/+question/694428
The proposal is to turn on LTO by default on most 64bit release architectures.
On Fri, Jun 17, 2022 at 10:18:43AM +0200, Matthias Klose wrote:...
...
Link time
optimizations are also at least turned on in other distros like Fedora, OpenSuse (two years) and Ubuntu (one year).
...
The idea is to file wishlist bug reports for those 373 packages and then see
how far we get, and if it's feasible to already turn on LTO for bookworm. If not, it should be turned on by default for the following release.
I assume these 373 packages have already been fixed/workarounded in Ubuntu? Submitting 373 bugs with patches should settle the feasibility question.
A bigger worry is the schedule of such a change.
A major toolchain change shortly before the freeze means the vast
majority of packages will be shipped with non-LTO builds in the release,
with security updates or point release updates triggering a change to
an LTO built package.
This means few packages actually benefitting from LTO, but a higher regression risk when fixing bugs in stable.
The best timing for such a change would be immediately after the release
of bookworm.
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