svn commit: r253460 - head/sys/dev/mps

[Scott Long]

Thanks, I'll look into it.

Scott

On Aug 11, 2013, at 6:01 AM, Alexander Motin <mav at FreeBSD.org> wrote:

> On 19.07.2013 03:12, Scott Long wrote:
>> Author: scottl
>> Date: Fri Jul 19 00:12:41 2013
>> New Revision: 253460
>> URL: http://svnweb.freebsd.org/changeset/base/253460
>> 
>> Log:
>>   Overhaul error, information, and debug logging.
>> 
>>   Obtained from:	Netflix
>>   MFC after:	3 days
>> 
>> Modified:
>>   head/sys/dev/mps/mps.c
>>   head/sys/dev/mps/mps_mapping.c
>>   head/sys/dev/mps/mps_pci.c
>>   head/sys/dev/mps/mps_sas.c
>>   head/sys/dev/mps/mps_sas_lsi.c
>>   head/sys/dev/mps/mps_table.c
>>   head/sys/dev/mps/mps_user.c
>>   head/sys/dev/mps/mpsvar.h
> 
> This change created significant CPU overhead under high I/O rate (350K IOPS) because several functions inside mpssas_log_command() are now writing into the buffer that is just discarded after that. The following simple patch seems fixes the situation for me:
> 
> Index: mps_sas.c
> ===================================================================
> --- mps_sas.c   (revision 254181)
> +++ mps_sas.c   (working copy)
> @@ -304,7 +304,7 @@ mpssas_log_command(struct mps_command *cm, u_int l
>        char str[192];
>        char path_str[64];
> 
> -       if (cm == NULL)
> +       if (cm == NULL || (cm->cm_sc->mps_debug & level) == 0)
>                return;
> 
>        sbuf_new(&sb, str, sizeof(str), 0);
> 
> 
> -- 
> Alexander Motin