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'''
Performance Metrics Domain Agent exporting Linux compressed swap metrics.
'''
#
# Copyright (c) 2014 Red Hat.
#
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
# for more details.
#
import cpmapi as c_api
from pcp.pmapi import pmUnits
from pcp.pmda import PMDA, pmdaMetric, pmdaIndom
from resource import getpagesize
from os import getenv, listdir
ZSWAP_PAGESIZE = getpagesize()
ZSWAP_STATS_PATH = '/sys/kernel/debug/zswap'
class ZswapPMDA(PMDA):
'''
Performance Metrics Domain Agent exporting compressed swap metrics.
Install it and make basic use of it if you use zswap, as follows:
# $PCP_PMDAS_DIR/zswap/Install
$ pminfo -fmdtT zswap
'''
def zswap_fetch_single(self, name):
''' Extract one value from a single zswap statistics file. '''
fullpath = self.path + '/' + name
try:
with open(fullpath) as file:
value = file.readline()
self.values[name] = long(value)
except:
# use a simple approach to avoiding errors on every fetch
if self.fileerrors < self.nmetrics:
self.err("fetch_single: failed to read %s" % fullpath)
self.fileerrors += 1
pass
def zswap_fetch(self):
'''
Called once per PCP "fetch" PDU from pmcd(1)
Iterates over the (sysfs debug) path holding zswap statistics,
building a hash of values (one value extracted from each file).
'''
# self.log("fetch: %s" % self.path)
try:
self.patherrors = 0
files = listdir(self.path)
for name in files:
self.zswap_fetch_single(name)
except:
# the kernel module may simply not be loaded currently
self.patherrors = 1
pass
def zswap_fetch_callback(self, cluster, item, inst):
'''
Main fetch callback - looks up value associated with requested PMID
(from zswap_fetch), converts units if needed, then returns a list of
value,status (single pair) for the requested pmid
'''
# self.log("fetch callback for %d.%d[%d]" % (cluster, item, inst))
if inst != c_api.PM_IN_NULL:
return [c_api.PM_ERR_INST, 0]
elif cluster != 0:
return [c_api.PM_ERR_PMID, 0]
if item >= 0 and item < self.nmetrics and self.patherrors == 1:
return [c_api.PM_ERR_AGAIN, 0]
if item == 0:
return [self.values['pool_limit_hit'], 1]
elif item == 1:
return [self.values['reject_reclaim_fail'], 1]
elif item == 2:
return [self.values['reject_alloc_fail'], 1]
elif item == 3:
return [self.values['reject_kmemcache_fail'], 1]
elif item == 4:
return [self.values['reject_compress_poor'], 1]
elif item == 5:
return [self.values['written_back_pages'] * self.pagesize, 1]
elif item == 6:
return [self.values['duplicate_entry'], 1]
elif item == 7:
return [self.values['pool_pages'] * self.pagesize, 1]
elif item == 8:
return [self.values['stored_pages'] * self.pagesize, 1]
return [c_api.PM_ERR_PMID, 0]
def setup_zswap_metrics(self, name):
'''
Setup the metric table - ensure a values hash entry is setup for
each metric; that way we don't need to worry about KeyErrors in
the fetch callback routine (e.g. if the kernel interface changes).
'''
self.values['pool_limit_hit'] = 0
self.add_metric(name + '.pool_limit_hit', pmdaMetric(
self.pmid(0, 0),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Pool limit was hit (see zswap_max_pool_percent module parameter)')
self.values['reject_reclaim_fail'] = 0
self.add_metric(name + '.reject_reclaim_fail', pmdaMetric(
self.pmid(0, 1),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Store failed due to a reclaim failure after pool limit was reached')
self.values['reject_alloc_fail'] = 0
self.add_metric(name + '.reject_alloc_fail', pmdaMetric(
self.pmid(0, 2),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Store failed because underlying allocator could not get memory')
self.values['reject_kmemcache_fail'] = 0
self.add_metric(name + '.reject_kmemcache_fail', pmdaMetric(
self.pmid(0, 3),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Store failed because the entry metadata could not be allocated (rare)')
self.values['reject_compress_poor'] = 0
self.add_metric(name + '.reject_compress_poor', pmdaMetric(
self.pmid(0, 4),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Compressed page was too big for the allocator to (optimally) store')
self.values['written_back_pages'] = 0
self.add_metric(name + '.written_back_pages', pmdaMetric(
self.pmid(0, 5),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(1, 0, 0, c_api.PM_SPACE_KBYTE, 0, 0)),
'Pages written back when pool limit was reached')
self.values['duplicate_entry'] = 0
self.add_metric(name + '.duplicate_entry', pmdaMetric(
self.pmid(0, 6),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(0, 0, 1, 0, 0, c_api.PM_COUNT_ONE)),
'Duplicate store was encountered (rare)')
self.values['pool_pages'] = 0
self.add_metric(name + '.pool_pages', pmdaMetric(
self.pmid(0, 7),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(1, 0, 0, c_api.PM_SPACE_KBYTE, 0, 0)),
'Memory pages used by the compressed pool')
self.values['stored_pages'] = 0
self.add_metric(name + '.stored_pages', pmdaMetric(
self.pmid(0, 8),
c_api.PM_TYPE_U64, c_api.PM_INDOM_NULL, c_api.PM_SEM_COUNTER,
pmUnits(1, 0, 0, c_api.PM_SPACE_KBYTE, 0, 0)),
'Compressed pages currently stored in zswap')
def __init__(self, name, domain):
PMDA.__init__(self, name, domain)
self.patherrors = 0
self.fileerrors = 0
self.pagesize = int(getenv('ZSWAP_PAGESIZE', ZSWAP_PAGESIZE))
self.path = str(getenv('ZSWAP_STATS_PATH', ZSWAP_STATS_PATH))
self.values = {}
self.setup_zswap_metrics(name)
self.nmetrics = len(self.values)
self.set_fetch(self.zswap_fetch)
self.set_fetch_callback(self.zswap_fetch_callback)
if __name__ == '__main__':
ZswapPMDA('zswap', 125).run()
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