Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-11 Thread Ingo Molnar
* Frederic Weisbecker wrote: > > I'm worried about the proliferation of not easily separable > > config options. We already have way too many timer and > > scheduler options to begin with. > > Like Steve said, this is for overhead reasons. The syscall > uses the slow path so that's ok. But

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-11 Thread Ingo Molnar
* Frederic Weisbecker fweis...@gmail.com wrote: I'm worried about the proliferation of not easily separable config options. We already have way too many timer and scheduler options to begin with. Like Steve said, this is for overhead reasons. The syscall uses the slow path so that's

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Christoph Lameter
On Fri, 8 Feb 2013, Clark Williams wrote: > I was a little apprehensive when you started talking about multiple > tasks in Adaptive NOHZ mode on a core but the more I started thinking > about it, I realized that we might end up in a cooperative multitasking > mode with no tick at all going.

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Clark Williams
On Fri, 8 Feb 2013 16:53:17 +0100 Frederic Weisbecker wrote: > 2013/2/7 Christoph Lameter : > > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > > > >> Not with hrtick. > > > > hrtick? Did we not already try that a couple of years back and it turned > > out that the overhead of constantly

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Christoph Lameter
On Fri, 8 Feb 2013, Steven Rostedt wrote: > On Fri, 2013-02-08 at 16:53 +0100, Frederic Weisbecker wrote: > > 2013/2/7 Christoph Lameter : > > > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > > > > > >> Not with hrtick. > > > > > > hrtick? Did we not already try that a couple of years back and

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Steven Rostedt
On Fri, 2013-02-08 at 16:53 +0100, Frederic Weisbecker wrote: > 2013/2/7 Christoph Lameter : > > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > > > >> Not with hrtick. > > > > hrtick? Did we not already try that a couple of years back and it turned > > out that the overhead of constantly

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Frederic Weisbecker
2013/2/7 Christoph Lameter : > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > >> Not with hrtick. > > hrtick? Did we not already try that a couple of years back and it turned > out that the overhead of constantly reprogramming a timer via the PCI bus > was causing too much of a performance

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Frederic Weisbecker
2013/2/7 Ingo Molnar : > > * Frederic Weisbecker wrote: > >> 2013/2/7 Ingo Molnar : >> > >> > * Steven Rostedt wrote: >> > >> >> I'll reply to this as I come up with comments. >> >> >> >> First thing is, don't call it NO_HZ_FULL. A better name would >> >> be NO_HZ_CPU. I would like to reserve

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Frederic Weisbecker
2013/2/7 Ingo Molnar mi...@kernel.org: * Frederic Weisbecker fweis...@gmail.com wrote: 2013/2/7 Ingo Molnar mi...@kernel.org: * Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Frederic Weisbecker
2013/2/7 Christoph Lameter c...@linux.com: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly reprogramming a timer via the PCI bus was causing too much of a performance

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Steven Rostedt
On Fri, 2013-02-08 at 16:53 +0100, Frederic Weisbecker wrote: 2013/2/7 Christoph Lameter c...@linux.com: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Christoph Lameter
On Fri, 8 Feb 2013, Steven Rostedt wrote: On Fri, 2013-02-08 at 16:53 +0100, Frederic Weisbecker wrote: 2013/2/7 Christoph Lameter c...@linux.com: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Clark Williams
On Fri, 8 Feb 2013 16:53:17 +0100 Frederic Weisbecker fweis...@gmail.com wrote: 2013/2/7 Christoph Lameter c...@linux.com: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-08 Thread Christoph Lameter
On Fri, 8 Feb 2013, Clark Williams wrote: I was a little apprehensive when you started talking about multiple tasks in Adaptive NOHZ mode on a core but the more I started thinking about it, I realized that we might end up in a cooperative multitasking mode with no tick at all going. Multiple

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Mike Galbraith
On Thu, 2013-02-07 at 19:14 +, Christoph Lameter wrote: > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > > > Not with hrtick. > > hrtick? Did we not already try that a couple of years back and it turned > out that the overhead of constantly reprogramming a timer via the PCI bus > was

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Christoph Lameter wrote: > On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > > > Not with hrtick. > > hrtick? Did we not already try that a couple of years back and > it turned out that the overhead of constantly reprogramming a > timer via the PCI bus was causing too much of a performance

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 20:07 +0100, Ingo Molnar wrote: > Could we just simplify things and make this an unconditional > option of NO_HZ? Any reason why we'd want to make this > configurable, other than debugging? I think the worry is the overhead that is required to keep it active. It requires

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Christoph Lameter
On Thu, 7 Feb 2013, Frederic Weisbecker wrote: > Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly reprogramming a timer via the PCI bus was causing too much of a performance regression? -- To unsubscribe from this list:

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Frederic Weisbecker wrote: > 2013/2/7 Ingo Molnar : > > > > * Steven Rostedt wrote: > > > >> I'll reply to this as I come up with comments. > >> > >> First thing is, don't call it NO_HZ_FULL. A better name would > >> be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we > >> totally

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt : > On Thu, 2013-02-07 at 17:45 +0100, Frederic Weisbecker wrote: > >> > >> > config NO_HZ_TASK >> > bool "Stop tick on specified CPUs when single task is running" >> > default n >> > depends on NO_HZ >> >> Ok I launched another debate about that

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Paul E. McKenney
On Thu, Feb 07, 2013 at 12:06:21PM -0500, Steven Rostedt wrote: > On Thu, 2013-02-07 at 08:30 -0800, Paul E. McKenney wrote: > > > I suspect that removal of jiffies from the kernel will take a few stages, > > with RCU being one of the laggards for awhile. Making RCU's state > > machine depend

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt : > On Thu, 2013-02-07 at 17:41 +0100, Frederic Weisbecker wrote: > >> I'm not convinced that "single task" must be a fundamental component >> of this. It's an implementation detail. We should be able to keep the >> tick off in the future when more than one task are on the

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 08:30 -0800, Paul E. McKenney wrote: > I suspect that removal of jiffies from the kernel will take a few stages, > with RCU being one of the laggards for awhile. Making RCU's state > machine depend wholly on process-based execution will take some care > and experimentation,

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:45 +0100, Frederic Weisbecker wrote: > > > > config NO_HZ_TASK > > bool "Stop tick on specified CPUs when single task is running" > > default n > > depends on NO_HZ > > Ok I launched another debate about that single task thing. I wish we > don't

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:41 +0100, Frederic Weisbecker wrote: > I'm not convinced that "single task" must be a fundamental component > of this. It's an implementation detail. We should be able to keep the > tick off in the future when more than one task are on the runqueue and > hrtick is on. May

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Paul E. McKenney
On Thu, Feb 07, 2013 at 11:12:00AM -0500, Steven Rostedt wrote: > On Thu, 2013-02-07 at 12:10 +0100, Ingo Molnar wrote: > > * Steven Rostedt wrote: > > > > > I'll reply to this as I come up with comments. > > > > > > First thing is, don't call it NO_HZ_FULL. A better name would > > > be

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt : > On Thu, 2013-02-07 at 17:25 +0100, Frederic Weisbecker wrote: > >> At least for now we seem to agree on CONFIG_NO_HZ_IDLE and keep >> CONFIG_NO_HZ for compatibility. Are you ok with that? If so I'll send >> a patch. > > I believe that Ingo was suggesting to have

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt : > I'll reply to this as I come up with comments. > > First thing is, don't call it NO_HZ_FULL. A better name would be > NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove > jiffies :-) I'm not sure we'll ever be able to completely remove the tick, even

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:25 +0100, Frederic Weisbecker wrote: > At least for now we seem to agree on CONFIG_NO_HZ_IDLE and keep > CONFIG_NO_HZ for compatibility. Are you ok with that? If so I'll send > a patch. I believe that Ingo was suggesting to have CONFIG_NO_HZ give options to what type of

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Ingo Molnar : > > * Steven Rostedt wrote: > >> I'll reply to this as I come up with comments. >> >> First thing is, don't call it NO_HZ_FULL. A better name would >> be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we >> totally remove jiffies :-) > > I don't think we want yet

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 12:10 +0100, Ingo Molnar wrote: > * Steven Rostedt wrote: > > > I'll reply to this as I come up with comments. > > > > First thing is, don't call it NO_HZ_FULL. A better name would > > be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we > > totally remove jiffies

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Christoph Lameter
On Thu, 7 Feb 2013, Ingo Molnar wrote: > Agreed? Yes and please also change the texts in Kconfig to accurately describe what happens to the timer tick. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Steven Rostedt wrote: > I'll reply to this as I come up with comments. > > First thing is, don't call it NO_HZ_FULL. A better name would > be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we > totally remove jiffies :-) I don't think we want yet another config option named in a

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Frederic Weisbecker fweis...@gmail.com wrote: 2013/2/7 Ingo Molnar mi...@kernel.org: * Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Christoph Lameter
On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly reprogramming a timer via the PCI bus was causing too much of a performance regression? -- To unsubscribe from this list:

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 20:07 +0100, Ingo Molnar wrote: Could we just simplify things and make this an unconditional option of NO_HZ? Any reason why we'd want to make this configurable, other than debugging? I think the worry is the overhead that is required to keep it active. It requires the

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Christoph Lameter c...@linux.com wrote: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly reprogramming a timer via the PCI bus was causing too much of a

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Mike Galbraith
On Thu, 2013-02-07 at 19:14 +, Christoph Lameter wrote: On Thu, 7 Feb 2013, Frederic Weisbecker wrote: Not with hrtick. hrtick? Did we not already try that a couple of years back and it turned out that the overhead of constantly reprogramming a timer via the PCI bus was causing too

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Ingo Molnar
* Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove jiffies :-) I don't think we want yet another config option

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Christoph Lameter
On Thu, 7 Feb 2013, Ingo Molnar wrote: Agreed? Yes and please also change the texts in Kconfig to accurately describe what happens to the timer tick. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 12:10 +0100, Ingo Molnar wrote: * Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Ingo Molnar mi...@kernel.org: * Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove jiffies :-) I don't

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:25 +0100, Frederic Weisbecker wrote: At least for now we seem to agree on CONFIG_NO_HZ_IDLE and keep CONFIG_NO_HZ for compatibility. Are you ok with that? If so I'll send a patch. I believe that Ingo was suggesting to have CONFIG_NO_HZ give options to what type of

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt rost...@goodmis.org: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove jiffies :-) I'm not sure we'll ever be able to completely remove

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt rost...@goodmis.org: On Thu, 2013-02-07 at 17:25 +0100, Frederic Weisbecker wrote: At least for now we seem to agree on CONFIG_NO_HZ_IDLE and keep CONFIG_NO_HZ for compatibility. Are you ok with that? If so I'll send a patch. I believe that Ingo was suggesting to

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Paul E. McKenney
On Thu, Feb 07, 2013 at 11:12:00AM -0500, Steven Rostedt wrote: On Thu, 2013-02-07 at 12:10 +0100, Ingo Molnar wrote: * Steven Rostedt rost...@goodmis.org wrote: I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:41 +0100, Frederic Weisbecker wrote: I'm not convinced that single task must be a fundamental component of this. It's an implementation detail. We should be able to keep the tick off in the future when more than one task are on the runqueue and hrtick is on. May be

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 17:45 +0100, Frederic Weisbecker wrote: config NO_HZ_TASK bool Stop tick on specified CPUs when single task is running default n depends on NO_HZ Ok I launched another debate about that single task thing. I wish we don't make it a

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Steven Rostedt
On Thu, 2013-02-07 at 08:30 -0800, Paul E. McKenney wrote: I suspect that removal of jiffies from the kernel will take a few stages, with RCU being one of the laggards for awhile. Making RCU's state machine depend wholly on process-based execution will take some care and experimentation,

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt rost...@goodmis.org: On Thu, 2013-02-07 at 17:41 +0100, Frederic Weisbecker wrote: I'm not convinced that single task must be a fundamental component of this. It's an implementation detail. We should be able to keep the tick off in the future when more than one task

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Paul E. McKenney
On Thu, Feb 07, 2013 at 12:06:21PM -0500, Steven Rostedt wrote: On Thu, 2013-02-07 at 08:30 -0800, Paul E. McKenney wrote: I suspect that removal of jiffies from the kernel will take a few stages, with RCU being one of the laggards for awhile. Making RCU's state machine depend wholly on

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-07 Thread Frederic Weisbecker
2013/2/7 Steven Rostedt rost...@goodmis.org: On Thu, 2013-02-07 at 17:45 +0100, Frederic Weisbecker wrote: config NO_HZ_TASK bool Stop tick on specified CPUs when single task is running default n depends on NO_HZ Ok I launched another debate about that single

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-06 Thread Steven Rostedt
I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove jiffies :-) And the kconfig help should probably call it "Adaptive tickless" or "Tickless for single tasks". The

[ANNOUNCE] 3.8-rc6-nohz4

2013-02-06 Thread Frederic Weisbecker
Hi, The support for printk and cputime accounting to work on full dynticks CPUs have been merged in -tip tree and is likely deemed for the 3.9 merge window. So this new release is a rebase against the relevant branches in -tip and v3.8-rc6. The remaining amount of patches has thus quite

[ANNOUNCE] 3.8-rc6-nohz4

2013-02-06 Thread Frederic Weisbecker
Hi, The support for printk and cputime accounting to work on full dynticks CPUs have been merged in -tip tree and is likely deemed for the 3.9 merge window. So this new release is a rebase against the relevant branches in -tip and v3.8-rc6. The remaining amount of patches has thus quite

Re: [ANNOUNCE] 3.8-rc6-nohz4

2013-02-06 Thread Steven Rostedt
I'll reply to this as I come up with comments. First thing is, don't call it NO_HZ_FULL. A better name would be NO_HZ_CPU. I would like to reserve NO_HZ_FULL when we totally remove jiffies :-) And the kconfig help should probably call it Adaptive tickless or Tickless for single tasks. The full