On Tue, May 7, 2013 at 9:59 AM, Artem S. Tashkinov <t.artem@xxxxxxxxx> wrote: > May 7, 2013 09:25:40 PM, Bjorn Helgaas wrote: >> [+cc Phillip] >> >>> I would suspect that Windows' complaint about the BIOS mucking up the MTRRs >>> is likely the best hint. Likely Windows is detecting the problem and fixing >>> it up on resume, thus it only complains about "reduced resume performance". >>> If the MTRRs are messed up, then quite likely parts of RAM have become >>> uncacheable, causing performance to get randomly slaughtered in various >>> ways. >>> >>> From looking at the code it's not clear if we are checking/restoring the >>> MTRR contents after resume. If not, maybe we should be. >> >>I agree; the MTRR warning is a good hint. Artem? >> >>Phillip, I cc'd you because you have similar hardware and your >>https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1131468 report is >>slightly similar. Have you seen anything like this "reduced >>performance after resume" issue? If so, can you collect /proc/mtrr >>contents before and after suspending? >> > > Like Robert Hancock correctly noted the Linux kernel lacks the code to check > for MTTR changes after resume - I'm not a kernel hacker to write such a code ;-) > > Likewise there's no code to see if RAM pages have become uncacheable - i.e > I've no idea how to check it either. > > According to /proc/mttr nothing changes on resume - only Windows detects > the discrepancy between MTTR regions on resume. dmesg contains no warnings > or errors (aside from usual ACPI SATA warnings - but they happen right on > boot - so I highly doubt the ACPI or SATA layers can be the culprit, since USB > exhibits a similar performance degradation). I'm not sure if reading /proc/mtrr actually reads the registers out of the CPU each time, or whether we just return the cached values we read out during initial boot-up. If the latter, then this output isn't really useful as there's no guarantee the values are still intact. > > In short, there's little to nothing that I can check. > > That bug report has nothing to do with my problem - my PC suspends and > resumes more or less correctly - everything works (albeit some parts don't > work as they should). That person also has a very outdated BIOS - 1904 from > 08/15/2011. I wouldn't be surprised if BIOS update solved his problem. > > Best regards, > > Artem -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
