如何解释性能iTLB负载，iTLB负载缺失 [英] how to interpret perf iTLB-loads,iTLB-load-misses

问题描述

我有一个测试用例，可以观察

I have a test case to observe perf iTLB-loads,iTLB-load-misses by

perf stat -e dTLB-loads,dTLB-load-misses,iTLB-loads,iTLB-load-misses -p 22479

并获得输出:

进程ID为"22479"的性能计数器统计信息:

Performance counter stats for process id '22479':

     1,262,817      dTLB-loads                                                  
        13,950      dTLB-load-misses          #    1.10% of all dTLB cache hits 
            75      iTLB-loads                                                  
         6,882      iTLB-load-misses          # 9176.00% of all iTLB cache hits 

   3.999720948 seconds time elapsed

我不知道如何仅解释75个iTLB负载，但是6 882个iTLB负载缺失?！

I have no idea how to interpret iTLB-loads only 75 but iTLB-load-misses 6,882 ?!

lscpu显示:2.10GHz @ Intel(R)Xeon(R)CPU E5-2620 v4

lscpu showes : Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz

我可以解释如下:

iTLB加载次数是(75 + 6882)次，有75次命中，但有6882次未命中吗?

do (75+6882) times of iTLB-loads , there are 75 times hits but 6882 times misses ?

ocperf.py list | wc -l
Downloading https://download.01.org/perfmon/mapfile.csv to mapfile.csv

Traceback (most recent call last):
File "/home/marschen/tools/pmu-tools-master/ocperf.py", line 1012, in <module>
emap = find_emap()
File "/home/marschen/tools/pmu-tools-master/ocperf.py", line 831, in find_emap
event_download.download(el, toget)
File "/home/marschen/tools/pmu-tools-master/event_download.py", line 105, in download
getfile(modelpath, dir, "mapfile.csv")
File "/home/marschen/tools/pmu-tools-master/event_download.py", line 86, in getfile
f = urlopen(url)
File "/usr/lib64/python2.7/urllib2.py", line 154, in urlopen
return opener.open(url, data, timeout)
File "/usr/lib64/python2.7/urllib2.py", line 431, in open
response = self._open(req, data)
File "/usr/lib64/python2.7/urllib2.py", line 449, in _open
'_open', req)
File "/usr/lib64/python2.7/urllib2.py", line 409, in _call_chain
result = func(*args)
File "/usr/lib64/python2.7/urllib2.py", line 1258, in https_open
context=self._context, check_hostname=self._check_hostname)
File "/usr/lib64/python2.7/urllib2.py", line 1211, in do_open
h.request(req.get_method(), req.get_selector(), req.data, headers)
File "/usr/lib64/python2.7/httplib.py", line 1017, in request
self._send_request(method, url, body, headers)
File "/usr/lib64/python2.7/httplib.py", line 1051, in _send_request
self.endheaders(body)
File "/usr/lib64/python2.7/httplib.py", line 1013, in endheaders
self._send_output(message_body)
File "/usr/lib64/python2.7/httplib.py", line 864, in _send_output
self.send(msg)
File "/usr/lib64/python2.7/httplib.py", line 826, in send
self.connect()
File "/usr/lib64/python2.7/httplib.py", line 1227, in connect
HTTPConnection.connect(self)
File "/usr/lib64/python2.7/httplib.py", line 807, in connect
self.timeout, self.source_address)
File "/usr/lib64/python2.7/socket.py", line 562, in create_connection
sock.connect(sa)
File "/usr/lib64/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)

推荐答案

在Broadwell处理器上，性能将iTLB-loads映射到ITLB_MISSES.STLB_HIT，这表示TLB查找事件错过了L1 ITLB但撞到了统一的TLB (c2)至ITLB_MISSES.MISS_CAUSES_A_WALK(代表所有页面尺寸)，这表示TLB查找事件同时丢失了所有页面尺寸的L1 ITLB和统一的TLB(导致页面遍历).因此，iTLB-load-misses可以大于或小于或等于iTLB-loads.它们是独立的事件.

On your Broadwell processor, perf maps iTLB-loads to ITLB_MISSES.STLB_HIT, which represents the event of a TLB lookup that misses the L1 ITLB but hits the unified TLB for all page sizes, and iTLB-load-misses to ITLB_MISSES.MISS_CAUSES_A_WALK, which represents the event of a TLB lookup that misses both the L1 ITLB and the unified TLB (causing a page walk) for all page sizes. Therefore, iTLB-load-misses can be larger or smaller than or equal to iTLB-loads. They are independent events.

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