Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

This is a reply to a thread from back in Nov 2016... Linus> The thing is, with function tracing, you *can* get the return value Linus> and arguments. Sure, you'll probably need to write eBPF and just Linus> attach it to that fentry call point, and yes, if something is inlined Linus> you're just

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

This is a reply to a thread from back in Nov 2016... Linus> The thing is, with function tracing, you *can* get the return value Linus> and arguments. Sure, you'll probably need to write eBPF and just Linus> attach it to that fentry call point, and yes, if something is inlined Linus> you're just

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Mon, Nov 28, 2016 at 03:46:51PM -0700, Ross Zwisler wrote: > On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote: > > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > > Tracepoints are the standard way to capture debugging and tracing > > > information in many parts of

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Mon, Nov 28, 2016 at 03:46:51PM -0700, Ross Zwisler wrote: > On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote: > > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > > Tracepoints are the standard way to capture debugging and tracing > > > information in many parts of

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote: > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > Tracepoints are the standard way to capture debugging and tracing > > information in many parts of the kernel, including the XFS and ext4 > > filesystems. Create a

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote: > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > Tracepoints are the standard way to capture debugging and tracing > > information in many parts of the kernel, including the XFS and ext4 > > filesystems. Create a

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote: > On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote: > > > > And that's exactly why we need a method of marking tracepoints as > > stable. How else are we going to know whether a specific tracepoint > > is

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote: > On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote: > > > > And that's exactly why we need a method of marking tracepoints as > > stable. How else are we going to know whether a specific tracepoint > > is stable if the kernel code

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri 25-11-16 16:48:40, Ted Tso wrote: > On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > > We do have filesystem code that is just disgusting. As an example: > > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > > single function. If you want that, use the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri 25-11-16 16:48:40, Ted Tso wrote: > On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > > We do have filesystem code that is just disgusting. As an example: > > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > > single function. If you want that, use the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote: > You are living in some unrealistic dream-world where you think you can > get the right tracepoint on the first try. > > So there is no way in hell I would ever mark any tracepoint "stable" > until it has had a fair amount of use,

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote: > You are living in some unrealistic dream-world where you think you can > get the right tracepoint on the first try. > > So there is no way in hell I would ever mark any tracepoint "stable" > until it has had a fair amount of use,

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote: > > And that's exactly why we need a method of marking tracepoints as > stable. How else are we going to know whether a specific tracepoint > is stable if the kernel code doesn't document that it's stable? You are living

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote: > > And that's exactly why we need a method of marking tracepoints as > stable. How else are we going to know whether a specific tracepoint > is stable if the kernel code doesn't document that it's stable? You are living in some unrealistic

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote: > > > > My impression is that nobody (at least kernel-side) wants them to be > > a stable ABI, so long as nobody in userland screams about their code > >

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote: > > > > My impression is that nobody (at least kernel-side) wants them to be > > a stable ABI, so long as nobody in userland screams about their code > > being broken, everything is

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 1:48 PM, Theodore Ts'o wrote: > > There is a reason why people want to be able to do that, and that's > because kprobes doesn't give you access to the arguments and return > codes to the functions. Honestly, that's simply not a good reason. What if

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 1:48 PM, Theodore Ts'o wrote: > > There is a reason why people want to be able to do that, and that's > because kprobes doesn't give you access to the arguments and return > codes to the functions. Honestly, that's simply not a good reason. What if everybody did this? Do

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > We do have filesystem code that is just disgusting. As an example: > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > single function. If you want that, use the function tracer. That seems > to be just

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote: > We do have filesystem code that is just disgusting. As an example: > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > single function. If you want that, use the function tracer. That seems > to be just

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

> We do have filesystem code that is just disgusting. As an example: > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > single function. Hmmm... we have "gossip" statements in Orangefs which can be triggered with a debugfs knob... lots of functions have a gossip statement at

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

> We do have filesystem code that is just disgusting. As an example: > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every > single function. Hmmm... we have "gossip" statements in Orangefs which can be triggered with a debugfs knob... lots of functions have a gossip statement at

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote: > > My impression is that nobody (at least kernel-side) wants them to be > a stable ABI, so long as nobody in userland screams about their code > being broken, everything is fine. As usual, if nobody notices an ABI >

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote: > > My impression is that nobody (at least kernel-side) wants them to be > a stable ABI, so long as nobody in userland screams about their code > being broken, everything is fine. As usual, if nobody notices an ABI > change, it hasn't happened.

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 06:06:42PM +1100, Dave Chinner wrote: > > Tell that to Linus. You had been in the room, IIRC, when that had been > > brought up this year in Santa Fe. > > No, I wasn't at KS or plumbers, so this is all news to me. Sorry, thought you had been at KS ;-/ My apologies...

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 06:06:42PM +1100, Dave Chinner wrote: > > Tell that to Linus. You had been in the room, IIRC, when that had been > > brought up this year in Santa Fe. > > No, I wasn't at KS or plumbers, so this is all news to me. Sorry, thought you had been at KS ;-/ My apologies...

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 04:14:19AM +, Al Viro wrote: > [Linus Cc'd] > > On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote: > > > they have become parts of stable userland ABI and are to be maintained > > > indefinitely. Don't expect "tracepoints are special case" to prevent > > >

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Fri, Nov 25, 2016 at 04:14:19AM +, Al Viro wrote: > [Linus Cc'd] > > On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote: > > > they have become parts of stable userland ABI and are to be maintained > > > indefinitely. Don't expect "tracepoints are special case" to prevent > > >

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

[Linus Cc'd] On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote: > > they have become parts of stable userland ABI and are to be maintained > > indefinitely. Don't expect "tracepoints are special case" to prevent that. > > I call bullshit just like I always do when someone spouts this

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

[Linus Cc'd] On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote: > > they have become parts of stable userland ABI and are to be maintained > > indefinitely. Don't expect "tracepoints are special case" to prevent that. > > I call bullshit just like I always do when someone spouts this

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Thu, Nov 24, 2016 at 05:32:20PM +, Al Viro wrote: > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > Tracepoints are the standard way to capture debugging and tracing > > information in many parts of the kernel, including the XFS and ext4 > > filesystems. Create a

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Thu, Nov 24, 2016 at 05:32:20PM +, Al Viro wrote: > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > > Tracepoints are the standard way to capture debugging and tracing > > information in many parts of the kernel, including the XFS and ext4 > > filesystems. Create a

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed 23-11-16 11:44:19, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault

Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

On Wed 23-11-16 11:44:19, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault

[PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

Tracepoints are the standard way to capture debugging and tracing information in many parts of the kernel, including the XFS and ext4 filesystems. Create a tracepoint header for FS DAX and add the first DAX tracepoints to the PMD fault handler. This allows the tracing for DAX to be done in the

[PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing

Tracepoints are the standard way to capture debugging and tracing information in many parts of the kernel, including the XFS and ext4 filesystems. Create a tracepoint header for FS DAX and add the first DAX tracepoints to the PMD fault handler. This allows the tracing for DAX to be done in the