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Groups > linux.kernel > #1156983 > unrolled thread
| Started by | Andi Kleen <ak@linux.intel.com> |
|---|---|
| First post | 2015-06-03 01:40 +0200 |
| Last post | 2015-06-04 13:40 +0200 |
| Articles | 6 — 4 participants |
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Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Andi Kleen <ak@linux.intel.com> - 2015-06-03 01:40 +0200
Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Andy Lutomirski <luto@amacapital.net> - 2015-06-03 02:30 +0200
Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Andi Kleen <ak@linux.intel.com> - 2015-06-03 02:50 +0200
Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Andy Lutomirski <luto@amacapital.net> - 2015-06-03 03:00 +0200
Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Thomas Gleixner <tglx@linutronix.de> - 2015-06-03 18:30 +0200
Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() Adrian Hunter <adrian.hunter@intel.com> - 2015-06-04 13:40 +0200
| From | Andi Kleen <ak@linux.intel.com> |
|---|---|
| Date | 2015-06-03 01:40 +0200 |
| Subject | Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() |
| Message-ID | <px3WN-856-1@gated-at.bofh.it> |
On Tue, Jun 02, 2015 at 11:03:26PM +0200, Thomas Gleixner wrote: > > > On Tue, 2 Jun 2015, Andi Kleen wrote: > > > > There's the code in tsc_msr.c. It should be relatively > > > straightforward to extend it to cover everything that intel_pstate > > > supports. > > > > That's a good idea, but we still need an always working fallback when the > > model number is not available. So Adrian's patch is needed in any > > case. > > Nonsense. The slow calibration is already a working fallback. Please read Adrian's description again. It's not working when the PIT read is too slow. That is when the new algorithm is needed. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2015-06-03 02:30 +0200 |
| Subject | Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() |
| Message-ID | <px4Jb-OH-9@gated-at.bofh.it> |
| In reply to | #1156983 |
On Tue, Jun 2, 2015 at 4:38 PM, Andi Kleen <ak@linux.intel.com> wrote: > On Tue, Jun 02, 2015 at 11:03:26PM +0200, Thomas Gleixner wrote: >> >> >> On Tue, 2 Jun 2015, Andi Kleen wrote: >> >> > > There's the code in tsc_msr.c. It should be relatively >> > > straightforward to extend it to cover everything that intel_pstate >> > > supports. >> > >> > That's a good idea, but we still need an always working fallback when the >> > model number is not available. So Adrian's patch is needed in any >> > case. >> >> Nonsense. The slow calibration is already a working fallback. > > Please read Adrian's description again. It's not working when the PIT read is > too slow. That is when the new algorithm is needed. > tglx's suggestion was to use slow calibration as a fallback. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Andi Kleen <ak@linux.intel.com> |
|---|---|
| Date | 2015-06-03 02:50 +0200 |
| Message-ID | <px52y-1bs-15@gated-at.bofh.it> |
| In reply to | #1156997 |
On Tue, Jun 02, 2015 at 05:21:27PM -0700, Andy Lutomirski wrote: > On Tue, Jun 2, 2015 at 4:38 PM, Andi Kleen <ak@linux.intel.com> wrote: > > On Tue, Jun 02, 2015 at 11:03:26PM +0200, Thomas Gleixner wrote: > >> > >> > >> On Tue, 2 Jun 2015, Andi Kleen wrote: > >> > >> > > There's the code in tsc_msr.c. It should be relatively > >> > > straightforward to extend it to cover everything that intel_pstate > >> > > supports. > >> > > >> > That's a good idea, but we still need an always working fallback when the > >> > model number is not available. So Adrian's patch is needed in any > >> > case. > >> > >> Nonsense. The slow calibration is already a working fallback. > > > > Please read Adrian's description again. It's not working when the PIT read is > > too slow. That is when the new algorithm is needed. > > > > tglx's suggestion was to use slow calibration as a fallback. You mean the last fallback we have today? That one doesn't work if the PIT read is too slow. And Adrian's patch is fixing that. -Andi -- ak@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2015-06-03 03:00 +0200 |
| Subject | Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() |
| Message-ID | <px5ce-1n6-3@gated-at.bofh.it> |
| In reply to | #1157003 |
On Tue, Jun 2, 2015 at 5:39 PM, Andi Kleen <ak@linux.intel.com> wrote: > On Tue, Jun 02, 2015 at 05:21:27PM -0700, Andy Lutomirski wrote: >> On Tue, Jun 2, 2015 at 4:38 PM, Andi Kleen <ak@linux.intel.com> wrote: >> > On Tue, Jun 02, 2015 at 11:03:26PM +0200, Thomas Gleixner wrote: >> >> >> >> >> >> On Tue, 2 Jun 2015, Andi Kleen wrote: >> >> >> >> > > There's the code in tsc_msr.c. It should be relatively >> >> > > straightforward to extend it to cover everything that intel_pstate >> >> > > supports. >> >> > >> >> > That's a good idea, but we still need an always working fallback when the >> >> > model number is not available. So Adrian's patch is needed in any >> >> > case. >> >> >> >> Nonsense. The slow calibration is already a working fallback. >> > >> > Please read Adrian's description again. It's not working when the PIT read is >> > too slow. That is when the new algorithm is needed. >> > >> >> tglx's suggestion was to use slow calibration as a fallback. > > You mean the last fallback we have today? > > That one doesn't work if the PIT read is too slow. > > And Adrian's patch is fixing that. Then the changelog should say that I think. The current text says "Fast TSC calibration will always fail", which, to me, suggests that either the slow calibration will work or that the changelog message should be changed. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Thomas Gleixner <tglx@linutronix.de> |
|---|---|
| Date | 2015-06-03 18:30 +0200 |
| Message-ID | <pxjIf-6rK-23@gated-at.bofh.it> |
| In reply to | #1157007 |
On Wed, 3 Jun 2015, Adrian Hunter wrote: > On 03/06/15 06:30, Andi Kleen wrote: > >> Then the changelog should say that I think. The current text says > >> "Fast TSC calibration will always fail", which, to me, suggests that > >> either the slow calibration will work or that the changelog message > >> should be changed. > > > > Ok. No, the slow calibration works I believe. > > Yeah, so the (only?) downside is the 50ms wasted on Fast TSC > calibration. What about this? I'm certainly happy to apply this one. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Adrian Hunter <adrian.hunter@intel.com> |
|---|---|
| Date | 2015-06-04 13:40 +0200 |
| Subject | Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() |
| Message-ID | <pxBF7-7YJ-5@gated-at.bofh.it> |
| In reply to | #1157007 |
On 03/06/15 16:45, Linus Torvalds wrote: > On Wed, Jun 3, 2015 at 1:13 AM, Adrian Hunter <adrian.hunter@intel.com> wrote: >> >> Yeah, so the (only?) downside is the 50ms wasted on Fast TSC >> calibration. What about this? > > That's certainly simpler. > > What platform is this? It's a prototype. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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