Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


On Fri, Jun 08, 2012 at 04:45:18PM +0200, Peter Zijlstra wrote:
> I was thinking about reload_store(), that seems to only reload ucode for
> a single cpu.

Ok.

> > > The 'bestestet' idea I came up with is doing the verify thing I have
> > > from a delayed work -- say 1 second into the future. That way, when
> > > there's lots of cpus they all try and enqueue the one work, which at
> > > the end executes only once, provided the entire update scan took less
> > > than the second.
> > 
> > You're saying, you want the last CPU that gets to update its microcode
> > gets to also run the delayed work...? Probably, I'd assume ucode update
> > on a single CPU takes less than a second IIUC.
> 
> Nah.. it'll probably be the first. But it doesn't matter which cpu does
> it. So the idea was:
> 
> static void intel_snb_verify_work(struct work_struct *work)
> {
> 	/* do the verify thing.. */
> }
> 
> static DECLARE_DELAYED_WORK(intel_snb_delayed_work, intel_snb_verify_ucode);
> 
> static int intel_snb_ucode_notifier(struct notifier_block *self,
>                                    unsigned long action, void *_uci)
> {
>         /*
>          * Since ucode cannot be down-graded, and no future ucode revision
>          * is known to break PEBS again, we're ok with MICROCODE_CAN_UPDATE.
>          */
> 
>         if (action == MICROCODE_UPDATED)
> 		schedule_delayed_work(&intel_snb_delayed_work, HZ);
> 
>         return NOTIFY_DONE;
> }
> 
> Thus it will queue the delayed work when the work isn't already queued
> for execution. Resulting in the work only happening once a second (at
> most).

Ok, this would probably work - the last cpu that schedules the work should
definitely see ucode version updated on all cpus.

Or, instead of doing the verify thing on each cpu, you could track which
is the last cpu to run the delayed work and do the verify thing only on
it (the other works simply remove a bit from a bitmask or whatever...).

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/


[Other Archives]     [Linux Kernel Newbies]     [Linux Driver Development]     [Fedora Kernel]     [Linux Kernel Testers]     [Linux SH]     [Linux Omap]     [Linux Kbuild]     [Linux Tape]     [Linux Input]     [Linux Kernel Janitors]     [Linux Kernel Packagers]     [Linux Doc]     [Linux Man Pages]     [Linux API]     [Linux Memory Management]     [Linux Modules]     [Linux Standards]     [Kernel Announce]     [Netdev]     [Git]     [Linux PCI]     Linux CAN Development     [Linux I2C]     [Linux RDMA]     [Linux NUMA]     [Netfilter]     [Netfilter Devel]     [SELinux]     [Bugtraq]     [FIO]     [Linux Perf Users]     [Linux Serial]     [Linux PPP]     [Linux ISDN]     [Linux Next]     [Kernel Stable Commits]     [Linux Tip Commits]     [Kernel MM Commits]     [Linux Security Module]     [AutoFS]     [Filesystem Development]     [Ext3 Filesystem]     [Linux bcache]     [Ext4 Filesystem]     [Linux BTRFS]     [Linux CEPH Filesystem]     [Linux XFS]     [XFS]     [Linux NFS]     [Linux CIFS]     [Ecryptfs]     [Linux NILFS]     [Linux Cachefs]     [Reiser FS]     [Initramfs]     [Linux FB Devel]     [Linux OpenGL]     [DRI Devel]     [Fastboot]     [Linux RT Users]     [Linux RT Stable]     [eCos]     [Corosync]     [Linux Clusters]     [LVS Devel]     [Hot Plug]     [Linux Virtualization]     [KVM]     [KVM PPC]     [KVM ia64]     [Linux Containers]     [Linux Hexagon]     [Linux Cgroups]     [Util Linux]     [Wireless]     [Linux Bluetooth]     [Bluez Devel]     [Ethernet Bridging]     [Embedded Linux]     [Barebox]     [Linux MMC]     [Linux IIO]     [Sparse]     [Smatch]     [Linux Arch]     [x86 Platform Driver]     [Linux ACPI]     [Linux IBM ACPI]     [LM Sensors]     [CPU Freq]     [Linux Power Management]     [Linmodems]     [Linux DCCP]     [Linux SCTP]     [ALSA Devel]     [Linux USB]     [Linux PA RISC]     [Linux Samsung SOC]     [MIPS Linux]     [IBM S/390 Linux]     [ARM Linux]     [ARM Kernel]     [ARM MSM]     [Tegra Devel]     [Sparc Linux]     [Linux Security]     [Linux Sound]     [Linux Media]     [Video 4 Linux]     [Linux IRDA Users]     [Linux for the blind]     [Linux RAID]     [Linux ATA RAID]     [Device Mapper]     [Linux SCSI]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Linux IDE]     [Linux SMP]     [Linux AXP]     [Linux Alpha]     [Linux M68K]     [Linux ia64]     [Linux 8086]     [Linux x86_64]     [Linux Config]     [Linux Apps]     [Linux MSDOS]     [Linux X.25]     [Linux Crypto]     [DM Crypt]     [Linux Trace Users]     [Linux Btrace]     [Linux Watchdog]     [Utrace Devel]     [Linux C Programming]     [Linux Assembly]     [Dash]     [DWARVES]     [Hail Devel]     [Linux Kernel Debugger]     [Linux gcc]     [Gcc Help]     [X.Org]     [Wine]

Add to Google Powered by Linux

[Older Kernel Discussion]     [Yosemite National Park Forum]     [Large Format Photos]     [Gimp]     [Yosemite Photos]     [Stuff]