[TLDR: I'm adding this report to the list of tracked Linux kernel regressions; the text you find below is based on a few templates paragraphs you might have encountered already in similar form. See link in footer if these mails annoy you.] On 13.11.23 16:42, James Hutchinson wrote: > Running here on an Intel NUC 8i3BEH Coffee Lake machine under Arch Linux. > > Connected to this machine I have 4x USB DVB Cards (2xDVBSky S960 > DVB-S2 adapters & 2xGeniatech T230 DVB-T2 adapters), and I stream TV > Channels around the house via Tvheadend. > > Since linux kernel v6.5 onwards I noticed a bad performance regression > whereby the streams are basically unstable. There are tons of > continuity errors in the Tvheadend logfile, and the picture and sound > are badly broken up as though the system is throttled or does not have > the bandwidth to cope with the streams. > > Sometimes the stream will work for a minute or so after reboot, before > then becoming unstable, and then seems to remain unstable until the > next cold reboot. > > I dropped back to v6.1 LTS (where everything is fine) and re-tested > following the release of v6.6... > ...the problem had not gone away so I performed a git bisect to > identify the culprit and found this to be: > > 804951203aa541ad6720c9726c173d18aeb3ab6b: platform/x86:intel/pmc: > Combine core_init() and core_configure() > > I can work around the issue by either reverting this commit or by > disabling CONFIG_INTEL_PMC_CORE and rebuilding the kernel manually, > either of which results in perfect DVB streaming once more. > > Happy to test any potential patches or otherwise provide further > information as required. Thanks for the report. To be sure the issue doesn't fall through the cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression tracking bot: #regzbot ^introduced 804951203aa541ad6720c9726 https://bugzilla.kernel.org/show_bug.cgi?id=218143 #regzbot title platform/x86/intel/pmc: bad performance regression whereby the TV streams are basically unstable #regzbot ignore-activity This isn't a regression? This issue or a fix for it are already discussed somewhere else? It was fixed already? You want to clarify when the regression started to happen? Or point out I got the title or something else totally wrong? Then just reply and tell me -- ideally while also telling regzbot about it, as explained by the page listed in the footer of this mail. Developers: When fixing the issue, remember to add 'Link:' tags pointing to the report (the parent of this mail). See page linked in footer for details. Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr That page also explains what to do if mails like this annoy you.
