On 6/26/2013 5:14 AM, Ingo Molnar wrote: > > * Nathan Zimmer <nzimmer@xxxxxxx> wrote: > >> perf seems to struggle with 512 cpus, but I did get some data. > > Btw., mind outlining in what way it struggles? > > Thanks, > > Ingo > I submitted some patches to Jason Wessel that updated the community support for KDB & NMI quite awhile ago that addressed the issues with perf and friends on UV. But I have not heard back from him in a couple of months. Is there a new maintainer for NMI/PERF/KDB etc.? The primary problem is that the current UV NMI handler is in the primary NMI notifier chain causing excessive reads of a register in the UV hub. When perf is running these approach the millions per second, and the MMIO read is not only expensive but also distrupts the primary HUB activities of directing NUMA traffic. Thus the system slows down considerably, and perf can even lose events. We've even updated the UV BIOS to make this a faster path but it needs the newer NMI handler to use it. Perhaps I should resubmit them directly to you? Thanks, Mike -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
