linux-kernel - Re: [PATCH v3 0/8] Generic IRQ entry/exit support for powerpc

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Message-ID: <aVyW1ZTkEPppRsuk@li-1a3e774c-28e4-11b2-a85c-acc9f2883e29.ibm.com>
Date: Tue, 6 Jan 2026 10:31:56 +0530
From: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        chleroy@...nel.org, oleg@...hat.com, kees@...nel.org,
        luto@...capital.net, wad@...omium.org, mchauras@...ux.ibm.com,
        thuth@...hat.com, akpm@...ux-foundation.org, macro@...am.me.uk,
        deller@....de, ldv@...ace.io, charlie@...osinc.com,
        segher@...nel.crashing.org, bigeasy@...utronix.de,
        peterz@...radead.org, namcao@...utronix.de, tglx@...utronix.de,
        kan.liang@...ux.intel.com, mark.barnett@....com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/8] Generic IRQ entry/exit support for powerpc

On Thu, Jan 01, 2026 at 02:37:41PM +0530, Shrikanth Hegde wrote:
> 
> 
> On 12/29/25 10:24 AM, Mukesh Kumar Chaurasiya wrote:
> > Adding support for the generic irq entry/exit handling for PowerPC. The
> > goal is to bring PowerPC in line with other architectures that already
> > use the common irq entry infrastructure, reducing duplicated code and
> > making it easier to share future changes in entry/exit paths.
> > 
> > This is slightly tested of ppc64le and ppc32.
> > 
> > The performance benchmarks are below:
> > 
> > perf bench syscall usec/op
> > 
> > | Syscall | Base       | New        | change % |
> > | ------- | ---------- | ---------- | -------- |
> > | basic   | 0.173212   | 0.133294   | -23.05   |
> > | execve  | 363.176190 | 357.148150 | -1.66    |
> > | fork    | 853.657880 | 840.268800 | -1.57    |
> > | getpgid | 0.174832   | 0.135372   | -22.57   |
> > 
> 
> Could you please add a description for whether its an improvement
> or regression.
> 
> Looking at it, it seems time taken for operation to complete. So it is
> an improvement. Seeing negative numbers one might think its a regression.
> 
Sure will add an explanation.
> Also, are these average numbers?
Yes, as there was very high run to run variation i took an avg of
100 runs.
> Could you get the numbers with preempt=lazy and with context tracking on?
Sure will do those too.

Regards,
Mukesh

> 
> > perf bench syscall ops/sec
> > 
> > | Syscall | Base    | New     | change % |
> > | ------- | ------- | ------- | -------- |
> > | basic   | 6006021 | 7502236 | +24.91   |
> > | execve  | 2753    | 2800    | +1.71    |
> > | fork    | 1171    | 1190    | +1.62    |
> > | getpgid | 5942117 | 7387040 | +24.32   |
> > 
> > IPI latency benchmark
> > 
> > | Metric         | Base (ns)     | Test (ns)     | change % |
> > | -------------- | ------------- | ------------- | -------- |
> > | Dry-run        | 206652.45     | 209317.37     | +1.29    |
> > | Self-IPI       | 3567895.23    | 3590444.77    | +0.63    |
> > | Normal IPI     | 148570416.17  | 148564173.40  | -0.00    |
> > | Broadcast IPI  | 4033489673.38 | 4007319512.62 | -0.65    |
> > | Broadcast lock | 4011023005.48 | 4010267885.93 | -0.02    |
> > 
> > 
>