On Thu, Jan 28, 2021 at 03:20:38PM +0200, Alexander Bokovoy wrote: > With today's OpenQA tests I can point out that using zram on 2048MB RAM > VMs actually breaks FreeIPA deployment: > https://openqa.fedoraproject.org/tests/763006#step/role_deploy_domain_controller/35 > > OpenQA uses 2048MB RAM for QEMU VMs and this was typically OK for > FreeIPA deployment with integrated CA and DNS server. Not anymore with > zram activated: > > Jan 27 21:17:47 fedora zram_generator::generator[25243]: Creating unit dev-zram0.swap (/dev/zram0 with 1384MB) > > which ends up eating 2/3rds of the whole memory budget and FreeIPA > installer fails: > > 2021-01-28T02:18:31Z DEBUG ipa-server-install was invoked with arguments [] and options: {'unattended': True, 'ip_addresses': None, 'domain_name': 'test.openqa.fedoraproject.org', 'realm_name': 'TEST.OPENQA.FEDORAPROJECT.ORG', 'host_name': None, 'ca_cert > 2021-01-28T02:18:31Z DEBUG IPA version 4.9.1-1.fc34 > 2021-01-28T02:18:31Z DEBUG IPA platform fedora > 2021-01-28T02:18:31Z DEBUG IPA os-release Fedora 34 (Server Edition Prerelease) > 2021-01-28T02:18:31Z DEBUG Available memory is 823529472B > ... > 2021-01-28T02:18:31Z DEBUG The ipa-server-install command failed, exception: ScriptError: Less than the minimum 1.2GB of RAM is available, 0.77GB available > 2021-01-28T02:18:31Z ERROR Less than the minimum 1.2GB of RAM is available, 0.77GB available > 2021-01-28T02:18:31Z ERROR The ipa-server-install command failed. See /var/log/ipaserver-install.log for more information Enabling zram doesn't really "take away memory", because no pre-allocation happens. If there is no physical swap, then adding zram0 should just shown additional swap space, so I don't think it could cause the check to fail. But if there is physical swap, the zram device is used with higher preference than the physical swap. So I think the explanation could be that the VM has a swap partition. Before, some pages would be swapped out to zram, and some would be swapped out to the "real" swap. The fraction of RAM used for compressed zram would be on the order of 25% (zram-fraction=0.5 multiplied by typical compression 2:1). But now the kernel sees more zram swap, so it inserts pages there, taking away more of RAM, instead of saving pages to disk. So more memory (maybe 50% RAM) is used for the unswappable compressed pages. But this shouldn't break things: if there is enough pressure, pages would be swapped out to the physical swap device too. Assuming that this guess is correct, the check that ipa-server-install is doing should be adjusted. It should use the total available memory (ram + all kinds of swap) in the check, and not just available uncompressed pages. Or if it wants to ignore disk-based swap for some reason, it should use ram + zram + in-memory-zwap in the check. It would be nice to see the output of 'swapon -s' and 'zramctl' and 'free' on that machine. > While we can ask Adam to increase memory in those VMs, 2GB RAM was our > (FreeIPA) recommended lower level target for home deployments with > Celeron or RPI4 systems. Now zram use will force those systems to be > unusable out of the box. That's certainly not the goal. The main goal of the Change is to support machines with less RAM, not require more RAM. Zbyszek _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
