Disregard: was Re: large intermittent latency spike 2.6.28 (and 2.6.27.10),bisect commit ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 -> Revert "sched_clock:prevent scd->clock from moving backwards"

From: Jayson King
Date: Wed Dec 31 2008 - 04:50:12 EST


I noticed large latency spikes in 2.6.28 (and 2.6.27.10) which would make the system unresponsive for minutes at a time (alt+Fn switching wouldn't even work) when the system is under load. I could trigger the latency by running a large make -j 3. Sometimes it would trigger in a few seconds other times it would take a few minutes.

I bisected it in 2.6.27.10 to d9a888b061f55534016d2d86a21639948312a117 -> Revert "sched_clock: prevent scd->clock from moving backwards" (ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 in 2.6.28) and reverting it in 2.6.28 make the latency spike go away. At least, so far no spike in over 24 hours.
Please disregard this. I just had a latency spike again, so this is not the change I'm looking for... I'll need to look for what is causing it again, apparently not only the make -j 3 I thought, and do another test.

Jayson

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