lkml.org 
[lkml]   [2010]   [Apr]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 11/12] perf, x86: implement AMD IBS event configuration
From
Robert,

Some more comments about model_spec.

> Except for the sample period IBS can only be set up with raw (model
> specific) config values and raw data samples. The event attributes for
> the syscall should be programmed like this (IBS_FETCH):
>
>        memset(&attr, 0, sizeof(attr));
>        attr.type        = PERF_TYPE_RAW;
>        attr.sample_type = PERF_SAMPLE_CPU | PERF_SAMPLE_RAW;
>        attr.config      = IBS_FETCH_CONFIG_DEFAULT
>        attr.config     |=
>                ((unsigned long long)MODEL_SPEC_TYPE_IBS_FETCH << 32)
>                & MODEL_SPEC_TYPE_MASK;
>        attr.model_spec  = 1;
>
Why do you need model_spec, in addition to your special encoding?

>  /*
> + * Model specific hardware events
> + *
> + * With the attr.model_spec bit set we can setup hardware events
> + * others than generic performance counters. A special PMU 64 bit
> + * config value can be passed through the perf_event interface. The
> + * concept of PMU model-specific arguments was practiced already in
> + * Perfmon2. The type of event (8 bits) is determinded from the config
> + * value too, bit 32-39 are reserved for this.
> + */
Isn't the config field big enough to encode all the information you need?
In the kernel, you could check bit 32-39 and based on host CPU determine
whether it refers to IBS or is a bogus value. I am trying to figure out what
model_spec buys you. I believe RAW does not mean the final value as
accepted by HW but a value that must be interpreted by the model-specific
code to eventually come up with a raw HW value. In the current code, the
RAW value is never passed as is, it is assembled from various bits and
pieces incl. attr.config of course.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2010-04-21 13:39    [W:0.143 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site