Re: x86 TSC time warp puzzle

2005-04-04 Thread Joe Korty
On Mon, Apr 04, 2005 at 09:59:22AM +0100, [EMAIL PROTECTED] wrote: > Jonathan Lundell wrote: > >Well, not actually a time warp, though it feels like one. > > > >I'm doing some real-time bit-twiddling in a driver, using the TSC to > >measure out delays on the order of hundreds of nanoseconds.

Re: x86 TSC time warp puzzle

2005-04-04 Thread P
Jonathan Lundell wrote: Well, not actually a time warp, though it feels like one. I'm doing some real-time bit-twiddling in a driver, using the TSC to measure out delays on the order of hundreds of nanoseconds. Because I want an upper limit on the delay, I disable interrupts around it. The

Re: x86 TSC time warp puzzle

2005-04-04 Thread P
Jonathan Lundell wrote: Well, not actually a time warp, though it feels like one. I'm doing some real-time bit-twiddling in a driver, using the TSC to measure out delays on the order of hundreds of nanoseconds. Because I want an upper limit on the delay, I disable interrupts around it. The

Re: x86 TSC time warp puzzle

2005-04-04 Thread Joe Korty
On Mon, Apr 04, 2005 at 09:59:22AM +0100, [EMAIL PROTECTED] wrote: Jonathan Lundell wrote: Well, not actually a time warp, though it feels like one. I'm doing some real-time bit-twiddling in a driver, using the TSC to measure out delays on the order of hundreds of nanoseconds. Because I

RE: x86 TSC time warp puzzle

2005-04-02 Thread Jonathan Lundell
At 3:13 AM -0500 4/2/05, Lee Revell wrote: On Fri, 2005-04-01 at 23:05 -0800, Pallipadi, Venkatesh wrote: It can be SMI happening in the platform. Typically BIOS uses some SMI > polling to handle some devices during early boot. Though 500 microseconds > sounds a bit too high. Nope, that sounds

RE: x86 TSC time warp puzzle

2005-04-02 Thread Lee Revell
On Fri, 2005-04-01 at 23:05 -0800, Pallipadi, Venkatesh wrote: > It can be SMI happening in the platform. Typically BIOS uses some SMI > polling > to handle some devices during early boot. Though 500 microseconds sounds > a > bit too high. > Nope, that sounds just about right. Buggy BIOSes

RE: x86 TSC time warp puzzle

2005-04-02 Thread Lee Revell
On Fri, 2005-04-01 at 23:05 -0800, Pallipadi, Venkatesh wrote: It can be SMI happening in the platform. Typically BIOS uses some SMI polling to handle some devices during early boot. Though 500 microseconds sounds a bit too high. Nope, that sounds just about right. Buggy BIOSes that

RE: x86 TSC time warp puzzle

2005-04-02 Thread Jonathan Lundell
At 3:13 AM -0500 4/2/05, Lee Revell wrote: On Fri, 2005-04-01 at 23:05 -0800, Pallipadi, Venkatesh wrote: It can be SMI happening in the platform. Typically BIOS uses some SMI polling to handle some devices during early boot. Though 500 microseconds sounds a bit too high. Nope, that sounds

RE: x86 TSC time warp puzzle

2005-04-01 Thread Pallipadi, Venkatesh
t;From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Jonathan Lundell >Sent: Friday, April 01, 2005 5:43 PM >To: LKML >Subject: x86 TSC time warp puzzle > >Well, not actually a time warp, though it feels like one. > >I'm doing some real-time bit-twi

x86 TSC time warp puzzle

2005-04-01 Thread Jonathan Lundell
Well, not actually a time warp, though it feels like one. I'm doing some real-time bit-twiddling in a driver, using the TSC to measure out delays on the order of hundreds of nanoseconds. Because I want an upper limit on the delay, I disable interrupts around it. The logic is something like:

RE: x86 TSC time warp puzzle

2005-04-01 Thread Pallipadi, Venkatesh
: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jonathan Lundell Sent: Friday, April 01, 2005 5:43 PM To: LKML Subject: x86 TSC time warp puzzle Well, not actually a time warp, though it feels like one. I'm doing some real-time bit-twiddling in a driver, using the TSC to measure out