282 lines
7.7 KiB
Groff
282 lines
7.7 KiB
Groff
.\" Copyright (c) 2005 Joseph Koshy. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" This software is provided by Joseph Koshy ``as is'' and
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.\" any express or implied warranties, including, but not limited to, the
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.\" implied warranties of merchantability and fitness for a particular purpose
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.\" are disclaimed. in no event shall Joseph Koshy be liable
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.\" for any direct, indirect, incidental, special, exemplary, or consequential
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.\" damages (including, but not limited to, procurement of substitute goods
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.\" or services; loss of use, data, or profits; or business interruption)
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.\" however caused and on any theory of liability, whether in contract, strict
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.\" liability, or tort (including negligence or otherwise) arising in any way
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.\" out of the use of this software, even if advised of the possibility of
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.\" such damage.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 1, 2005
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.Os
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.Dt PMCLOG 3
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.Sh NAME
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.Nm pmclog_open ,
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.Nm pmclog_close ,
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.Nm pmclog_read ,
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.Nm pmclog_feed
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.Nd parse event log data generated by
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.Xr hwpmc 4
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.Sh LIBRARY
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.Lb libpmc
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.Sh SYNOPSIS
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.In pmclog.h
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.Ft "void *"
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.Fn pmclog_open "int fd"
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.Ft void
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.Fn pmclog_close "void *cookie"
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.Ft int
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.Fn pmclog_read "void *cookie" "struct pmclog_ev *ev"
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.Ft int
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.Fn pmclog_feed "void *cookie" "char *data" "int len"
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.Sh DESCRIPTION
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These functions provide a way for application programs to extract
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events from an event stream generated by
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.Xr hwpmc 4 .
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.Pp
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A new event log parser is allocated using
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.Fn pmclog_open .
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Argument
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.Fa fd
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may be a file descriptor opened for reading if the event stream is
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present in a file, or the constant
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.Dv PMCLOG_FD_NONE
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for an event stream present in memory.
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This function returns a cookie that is passed into the other functions
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in this API set.
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.Pp
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Function
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.Fn pmclog_read
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returns the next available event in the event stream associated with
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argument
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.Fa cookie .
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Argument
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.Fa ev
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points to an event descriptor that which will contain the result of a
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successfully parsed event.
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.Pp
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An event descriptor returned by
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.Fn pmclog_read
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has the following structure:
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.Bd -literal
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struct pmclog_ev {
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enum pmclog_state pl_state; /* parser state after 'get_event()' */
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off_t pl_offset; /* byte offset in stream */
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size_t pl_count; /* count of records so far */
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struct timespec pl_ts; /* log entry timestamp */
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enum pmclog_type pl_type; /* log entry kind */
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union { /* log entry data */
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struct pmclog_ev_allocate pl_a;
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struct pmclog_ev_proccsw pl_c;
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struct pmclog_ev_dropnotify pl_d;
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struct pmclog_ev_procexit pl_e;
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struct pmclog_ev_initialize pl_i;
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struct pmclog_ev_pcsample pl_s;
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struct pmclog_ev_pmcattach pl_t;
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struct pmclog_ev_userdata pl_u;
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struct pmclog_ev_procexec pl_x;
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} pl_u;
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};
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.Ed
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.Pp
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The current state of the parser is recorded in
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.Va pl_state .
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This field can take on the following values:
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.Bl -tag -width ".Dv PMCLOG_REQUIRE_DATA"
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.It Dv PMCLOG_EOF
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(For file based parsers only)
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An end-of-file condition was encountered on the configured file
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descriptor.
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.It Dv PMCLOG_ERROR
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An error occurred during parsing.
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.It Dv PMCLOG_OK
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A complete event record was read into
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.Fa *ev .
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.It Dv PMCLOG_REQUIRE_DATA
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There was insufficient data in the event stream to assemble a complete
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event record.
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For memory based parsers, more data can be fed to the
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parser using function
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.Fn pmclog_feed .
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For file based parsers, function
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.Fn pmclog_read
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may be retried when data is available on the configured file
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descriptor.
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.El
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.Pp
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The rest of the event structure is valid only if field
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.Va pl_state
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contains
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.Dv PMCLOG_OK .
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Field
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.Va pl_offset
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contains the offset of the current record in the byte stream.
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Field
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.Va pl_count
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contains the serial number of this event.
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Field
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.Va pl_ts
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contains a timestamp with the system time when the event occurred.
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Field
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.Va pl_type
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denotes the kind of the event returned in argument
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.Fa *ev
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and is one of the following:
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.Bl -tag -width ".Dv PMCLOG_TYPE_PMCALLOCATE"
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.It Dv PMCLOG_TYPE_DROPNOTIFY
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a marker indicating that
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.Xr hwpmc 4
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had to drop data due to a resource constraint.
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.It Dv PMCLOG_TYPE_INITIALIZE
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an initialization record.
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This is usually the first record in a log file.
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.It Dv PMCLOG_TYPE_PCSAMPLE
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A record containing an instruction pointer sample.
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.It Dv PMCLOG_TYPE_PMCALLOCATE
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A record describing a PMC allocation operation.
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.It Dv PMCLOG_TYPE_PMCATTACH
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A record describing a PMC attach operation.
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.It Dv PMCLOG_TYPE_PROCCSW
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A record describing a PMC reading at the time of a process context switch.
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.It Dv PMCLOG_TYPE_PROCEXIT
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A record describing the accumulated PMC reading for a process at the
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time of
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.Xr _exit 2 .
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.It Dv PMCLOG_TYPE_PROCEXEC
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A record describing an
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.Xr execve 2
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by a target process.
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.It Dv PMCLOG_TYPE_USERDATA
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A record containing user data.
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.El
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.Pp
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Function
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.Fn pmclog_feed
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is used with parsers configured to parse memory based event streams.
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It is intended to be called when function
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.Fn pmclog_read
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indicates the need for more data by a returning
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.Dv PMCLOG_REQUIRE_DATA
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in field
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.Va pl_state
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of its event structure argument.
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Argument
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.Fa data
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points to the start of a memory buffer containing fresh event data.
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Argument
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.Fa len
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indicates the number of data bytes available.
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The memory range
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.Bq Fa data , Fa data No + Fa len
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must remain valid till the next time
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.Fn pmclog_read
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returns an error.
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It is an error to use
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.Fn pmclog_feed
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on a parser configured to parse file data.
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.Pp
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Function
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.Fn pmclog_close
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releases the internal state allocated by a prior call
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to
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.Fn pmclog_open .
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.Sh RETURN VALUES
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Function
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.Fn pmclog_open
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will return a
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.No non- Ns Dv NULL
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value if successful or
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.Dv NULL
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otherwise.
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.Pp
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Function
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.Fn pmclog_read
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will return 0 in case a complete event record was successfully read,
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or will return \-1 and will set the
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.Va pl_state
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field of the event record to the appropriate code in case of an error.
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.Pp
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Function
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.Fn pmclog_feed
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will return 0 on success or \-1 in case of failure.
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.Sh EXAMPLES
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A template for using the log file parsing API is shown below in pseudocode:
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.Bd -literal
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void *parser; /* cookie */
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struct pmclog_ev ev; /* parsed event */
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int fd; /* file descriptor */
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fd = open(filename, O_RDONLY); /* open log file */
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parser = pmclog_open(fd); /* initialize parser */
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if (parser == NULL)
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--handle an out of memory error--;
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/* read and parse data */
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while (pmclog_read(parser, &ev) == 0) {
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assert(ev.pl_state == PMCLOG_OK);
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/* process the event */
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switch (ev.pl_type) {
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case PMCLOG_TYPE_ALLOCATE:
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--process a pmc allocation record--
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break;
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case PMCLOG_TYPE_PROCCSW:
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--process a thread context switch record--
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break;
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case PMCLOG_TYPE_PCSAMPLE:
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--process a PC sample--
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break;
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--and so on--
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}
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}
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/* examine parser state */
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switch (ev.pl_state) {
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case PMCLOG_EOF:
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--normal termination--
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break;
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case PMCLOG_ERROR:
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--look at errno here--
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break;
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case PMCLOG_REQUIRE_DATA:
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--arrange for more data to be available for parsing--
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break;
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default:
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assert(0);
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/*NOTREACHED*/
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}
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pmclog_close(parser); /* cleanup */
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.Ed
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.Sh ERRORS
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A call to
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.Fn pmclog_init_parser
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may fail with any of the errors returned by
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.Xr malloc 3 .
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.Pp
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A call to
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.Fn pmclog_read
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for a file based parser may fail with any of the errors returned by
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.Xr read 2 .
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.Sh SEE ALSO
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.Xr read 2 ,
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.Xr malloc 3 ,
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.Xr pmc 3 ,
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.Xr hwpmc 4 ,
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.Xr pmcstat 8
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