Messages in this thread | | | Date | Thu, 5 Nov 2015 17:43:22 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip/locking/core v9 4/6] locking/pvqspinlock: Collect slowpath lock statistics |
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On Thu, Nov 05, 2015 at 11:29:29AM -0500, Waiman Long wrote: > On 11/02/2015 11:40 AM, Peter Zijlstra wrote: > >On Fri, Oct 30, 2015 at 07:26:35PM -0400, Waiman Long wrote: > >>This patch enables the accumulation of kicking and waiting related > >>PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration > >>option is selected. It also enables the collection of data which > >>enable us to calculate the kicking and wakeup latencies which have > >>a heavy dependency on the CPUs being used. > >> > >>The statistical counters are per-cpu variables to minimize the > >>performance overhead in their updates. These counters are exported > >>via the sysfs filesystem under the /sys/kernel/qlockstat directory. > >>When the corresponding sysfs files are read, summation and computing > >>of the required data are then performed. > >Why did you switch to sysfs? You can create custom debugfs files too. > > I was not aware of that capability. So you mean using debugfs_create_file() > using custom file_operations. Right?
Yep.
> That doesn't seem to be easier than > using sysfs. However, I can use that if you think it is better to use > debugfs.
Mostly I just wanted to point out that it was possible; you need not change to sysfs because debugfs lacks the capability.
But now that you ask, I think debugfs might be the better place, such statistics (and the proposed CONFIG symbol) are purely for debug purposes, right?
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