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SubjectRe: [PATCH v9 08/22] tracing: Add 'hist' event trigger command
Hi Tom,

On 2015/07/17 2:22, Tom Zanussi wrote:

> @@ -3782,6 +3785,32 @@ static const char readme_msg[] =
> "\t To remove a trigger with a count:\n"
> "\t echo '!<trigger>:0 > <system>/<event>/trigger\n"
> "\t Filters can be ignored when removing a trigger.\n"
> +#ifdef CONFIG_HIST_TRIGGERS
> + " hist trigger\t- If set, event hits are aggregated into a hash table\n"
> + "\t Format: hist:keys=<field1>\n"
> + "\t [:size=#entries]\n"
> + "\t [if <filter>]\n\n"
> + "\t When a matching event is hit, an entry is added to a hash\n"
> + "\t table using the key named. Keys correspond to fields in the\n"
> + "\t event's format description. On an event hit, the value of a\n"
> + "\t sum called 'hitcount' is incremented, which is simply a count\n"
> + "\t of event hits. Keys can be any field.\n\n"
> + "\t Reading the 'hist' file for the event will dump the hash\n"
> + "\t table in its entirety to stdout. Each printed hash table\n"
> + "\t entry is a simple list of the keys and values comprising the\n"
> + "\t entry; keys are printed first and are delineated by curly\n"
> + "\t braces, and are followed by the set of value fields for the\n"
> + "\t entry. Numeric fields are displayed as base-10 integers.\n"
> + "\t By default, the size of the hash table is 2048 entries. The\n"
> + "\t 'size' param can be used to specify more or fewer than that.\n"
> + "\t The units are in terms of hashtable entries - if a run uses\n"
> + "\t more entries than specified, the results will show the number\n"
> + "\t of 'drops', the number of hits that were ignored. The size\n"
> + "\t should be a power of 2 between 128 and 131072 (any non-\n"
> + "\t power-of-2 number specified will be rounded up).\n\n"
> + "\t The entries are sorted by 'hitcount' and the sort order is\n"
> + "\t 'ascending'.\n\n"


Hmm, this seems too much about implementation of histogram. Could you shorten this
to be a half ?


Thank you,


--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com


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