linux-kernel - Re: [patch V6 07/11] rseq: Implement time slice extension enforcement timer

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Message-ID: <20260127184820.GC3372621@noisy.programming.kicks-ass.net>
Date: Tue, 27 Jan 2026 19:48:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Prakash Sangappa <prakash.sangappa@...cle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>, Jonathan Corbet <corbet@....net>,
	Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Ron Geva <rongevarg@...il.com>, Waiman Long <longman@...hat.com>
Subject: Re: [patch V6 07/11] rseq: Implement time slice extension
 enforcement timer

On Fri, Jan 23, 2026 at 05:41:16PM +0000, Prakash Sangappa wrote:

> The database setup is on an older environment. The python script provided does not run as is.
> So, modified it to gather the stats by parsing trace-cmd report output.

I 'wrote' it against this thing:

  https://github.com/rostedt/trace-cmd/blob/master/python/tracecmd.py


> ========================================
> RSEQ SLICE HISTOGRAM (us)
> ========================================
> 
> Task: ora_dbwr_lmb-666257    Mean: 1593.058 ns
>   Latency (us)    | Count
>   ------------------------------
>   EXPIRED         | 3
>   0 us            | 8
>   1 us            | 116
>   2 us            | 25
>   3 us            | 2
>   4 us            | 1
>   7 us            | 1
> 
> Task: ora_dbwd_lmb-666196    Mean: 1548.641 ns
>   Latency (us)    | Count
>   ------------------------------
>   EXPIRED         | 6
>   0 us            | 19
>   1 us            | 203
>   2 us            | 33
>   4 us            | 2
>   5 us            | 1
> 
> 
> [..]
> 
> Task: oracle_668951_l-668951    Mean: 1797.796 ns
>   Latency (us)    | Count
>   ------------------------------
>   1 us            | 5
>   2 us            | 1
>   3 us            | 2
> 
> Task: oracle_671571_l-671571    Mean: 3285.425 ns
>   Latency (us)    | Count
>   ------------------------------
>   1 us            | 1
>   3 us            | 1
>   5 us            | 1
>   6 us            | 1
>   10 us           | 1
> 
> Task: oracle_672277_l-672277    Mean: 2361.600 ns
>   Latency (us)    | Count
>   ------------------------------
>   1 us            | 4
>   2 us            | 3
>   5 us            | 1
>   7 us            | 1
>   9 us            | 1
>   11 us           | 1
> 
> Task: ora_dbwb_lmb-666192    Mean: 1548.157 ns
>   Latency (us)    | Count
>   ------------------------------
>   EXPIRED         | 10
>   0 us            | 24
>   1 us            | 182
>   2 us            | 39
>   3 us            | 2
>   4 us            | 4
>   5 us            | 1
>   14 us           | 1

Thanks! that seems to confirm that 5us should be good enough for you
guys too.