RFR(XS): 8151030: PPC64: AllocatePrefetchStyle=4 is out of range

[Doerr, Martin]

Hi Götz, Michihiro and Lutz,

thanks for the reviews. Pushed.

Best regards,
Martin


> -----Original Message-----
> From: Schmidt, Lutz <lutz.schmidt at sap.com>
> Sent: Freitag, 24. April 2020 16:51
> To: Michihiro Horie <HORIE at jp.ibm.com>
> Cc: hotspot-compiler-dev at openjdk.java.net; Doerr, Martin
> <martin.doerr at sap.com>; ppc-aix-port-dev at openjdk.java.net
> Subject: Re: RFR(XS): 8151030: PPC64: AllocatePrefetchStyle=4 is out of range
> 
> Hi Martin,
> 
> SAP-internal testing revealed no problems related to this patch.
> 
> As Michihiro did not find performance issues, the patch is good to go from
> my perspective.
> 
> Regards,
> Lutz
> 
> From: Michihiro Horie <HORIE at jp.ibm.com> on behalf of Michihiro Horie
> <HORIE at jp.ibm.com>
> Date: Friday, 24. April 2020 at 07:40
> To: Lutz Schmidt <lutz.schmidt at sap.com>
> Cc: "hotspot-compiler-dev at openjdk.java.net" <hotspot-compiler-
> dev at openjdk.java.net>, "Doerr, Martin (martin.doerr at sap.com)"
> <martin.doerr at sap.com>, "ppc-aix-port-dev at openjdk.java.net" <ppc-aix-
> port-dev at openjdk.java.net>
> Subject: Re: RFR(XS): 8151030: PPC64: AllocatePrefetchStyle=4 is out of range
> 
> Hi Martin, Lutz,
> 
> I have not seen big differences in SPECjbb2015 scores both on P8 and P9.
> 
> Best regards,
> Michihiro
> 
> 
> ----- Original message -----
> From: "Schmidt, Lutz" <lutz.schmidt at sap.com>
> To: Michihiro Horie <HORIE at jp.ibm.com>, "Doerr, Martin"
> <martin.doerr at sap.com>
> Cc: "ppc-aix-port-dev at openjdk.java.net" <ppc-aix-port-
> dev at openjdk.java.net>, "hotspot-compiler-dev at openjdk.java.net"
> <hotspot-compiler-dev at openjdk.java.net>
> Subject: [EXTERNAL] Re: RFR(XS): 8151030: PPC64: AllocatePrefetchStyle=4 is
> out of range
> Date: Thu, Apr 23, 2020 3:01 AM
> 
> Hi Martin,
> 
> your change looks good to me.
> 
> I noticed you didn't find a chance to put it in the patch queue for our internal
> testing. I did that now, but it's too late for tonight. We'll have to wait until
> Friday morning (GMT+2) to really see what I expect: no issues.
> 
> Thanks for cleaning up this old stuff.
> 
> Regards,
> Lutz
> 
> 
> On 21.04.20, 16:57, "hotspot-compiler-dev on behalf of Michihiro Horie"
> <hotspot-compiler-dev-bounces at openjdk.java.net on behalf of
> HORIE at jp.ibm.com> wrote:
> 
> 
>     Hi Martin,
> 
>     I started measuring SPECjbb2015 to see the performance impact on P9.
> Also,
>     I'm preparing same measurement on P8.
> 
>     Best regards,
>     Michihiro
> 
> 
>      ----- Original message -----
>      From: "Doerr, Martin" <martin.doerr at sap.com>
>      To: "'hotspot-compiler-dev at openjdk.java.net'"
>      <hotspot-compiler-dev at openjdk.java.net>
>      Cc: Michihiro Horie <HORIE at jp.ibm.com>, "cjashfor at linux.ibm.com"
>      <cjashfor at linux.ibm.com>, "ppc-aix-port-dev at openjdk.java.net"
>      <ppc-aix-port-dev at openjdk.java.net>, Gustavo Romero
>      <gromero at linux.vnet.ibm.com>, "joserz at linux.ibm.com"
>      <joserz at linux.ibm.com>
>      Subject: [EXTERNAL] RFR(XS): 8151030: PPC64: AllocatePrefetchStyle=4 is
>      out of range
>      Date: Tue, Apr 14, 2020 11:07 PM
> 
>      Hi,
> 
>      I’d like to resolve a very old PPC64 issue:
>      https://bugs.openjdk.java.net/browse/JDK-8151030
> 
>      There’s code for AllocatePrefetchStyle=4 which is not an accepted option.
>      It was used for a special experimental prefetch mode using dcbz
>      instructions to combine prefetching and zeroing in the TLABs.
>      However, this code was never contributed and there are no plans to work
> on
>      it. So I’d like to simply remove this small part of it.
> 
>      In addition to that, AllocatePrefetchLines is currently set to 3 by
>      default which doesn’t make sense to me. PPC64 has an automatic prefetch
>      engine and executing several prefetch instructions for succeeding cache
>      lines doesn’t seem to be beneficial at all.
>      So I’m setting it to 1 by default. I couldn’t observe regressions on
>      Power7, Power8 and Power9.
> 
>      Webrev:
>      http://cr.openjdk.java.net/~mdoerr/8151030_ppc_prefetch/webrev.00/
> 
>      Please review.
> 
>      If somebody from IBM would like to check performance impact of
> changing
>      the AllocatePrefetchLines + Distance, I’ll be glad to receive feedback.
> 
>      Best regards,
>      Martin
> 
> 
> 
> 
>