PMC “unhalted-core-cycles” counted 'Branch Instruction Retired' [was: Fwd: svn commit: r272713 - head/sys/dev/hwpmc]

[Bjoern A. Zeeb]

Hi,

in case you have used “unhalted-core-cycles” for any PMC measurements in the last 17 months in HEAD or stable/10 (possibly more branches), you might want to go and re-visit your results.

In the interest of my research I’d appreciate if you could also drop me a private email (Reply-To set, don’t reply to all for this unless you want to) if this might have affected any of your work.

Best Regards,
Bjoern


Begin forwarded message:

> From: "Bjoern A. Zeeb" <bz at FreeBSD.org>
> Subject: svn commit: r272713 - head/sys/dev/hwpmc
> Date: 7 Oct 2014 18:00:35 GMT
> To: src-committers at freebsd.org, svn-src-all at freebsd.org, svn-src-head at freebsd.org
> 
> Author: bz
> Date: Tue Oct  7 18:00:34 2014
> New Revision: 272713
> URL: https://svnweb.freebsd.org/changeset/base/272713
> 
> Log:
>  Since introducing the extra mapping in r250103 for architectural performance
>  events we have actually counted 'Branch Instruction Retired' when people
>  asked for 'Unhalted core cycles' using the 'unhalted-core-cycles' event mask
>  mnemonic.
> 
>  Reviewed by:	jimharris
>  Discussed with:	gnn, rwatson
>  MFC after:	3 days
>  Sponsored by:	DARPA/AFRL
> 
> Modified:
>  head/sys/dev/hwpmc/hwpmc_core.c
> 
> Modified: head/sys/dev/hwpmc/hwpmc_core.c
> ==============================================================================
> --- head/sys/dev/hwpmc/hwpmc_core.c	Tue Oct  7 17:39:30 2014	(r272712)
> +++ head/sys/dev/hwpmc/hwpmc_core.c	Tue Oct  7 18:00:34 2014	(r272713)
> @@ -1796,7 +1796,7 @@ iap_is_event_architectural(enum pmc_even
> 	switch (pe) {
> 	case PMC_EV_IAP_ARCH_UNH_COR_CYC:
> 		ae = CORE_AE_UNHALTED_CORE_CYCLES;
> -		*map = PMC_EV_IAP_EVENT_C4H_00H;
> +		*map = PMC_EV_IAP_EVENT_3CH_00H;
> 		break;
> 	case PMC_EV_IAP_ARCH_INS_RET:
> 		ae = CORE_AE_INSTRUCTION_RETIRED;
> 

— 
Bjoern A. Zeeb             "Come on. Learn, goddamn it.", WarGames, 1983