latencytop深度了解你的Linux系统的延迟
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本文链接地址: latencytop深度了解你的Linux系统的延迟
我们在系统调优或者定位问题的时候,经常会发现多线程程序的效率很低,但是又不知道问题出在哪里,就知道上下文切换很多,但是为什么上下文切换,是谁导致切换,我们就不知道了。上下文切换可以用dstat这样的工具查看,比如:
$dstat ----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system-- usr sys idl wai hiq siq| read writ| recv send| in out | int csw 9 2 87 2 0 1|7398k 31M| 0 0 | 9.8k 11k| 16k 64k 20 4 69 3 0 4| 26M 56M| 34M 172M| 0 0 | 61k 200k 21 5 64 6 0 3| 26M 225M| 35M 175M| 0 0 | 75k 216k 21 5 66 4 0 4| 25M 119M| 34M 173M| 0 0 | 66k 207k 19 4 68 5 0 3| 23M 56M| 33M 166M| 0 0 | 60k 197k #或者用systemtap脚本来看 $sudo stap -e 'global cnt; probe scheduler.cpu_on {cnt<<<1;} probe timer.s(1){printf("%d\n", @count(cnt)); delete cnt;}' 217779 234141 234759
每秒高达200k左右的的上下文切换, 谁能告诉我发生了什么? 好吧,latencytop来救助了!
它的官网:http://www.latencytop.org/
Skipping audio, slower servers, everyone knows the symptoms of latency. But to know what’s going on in the system, what’s causing the latency, how to fix it… that’s a hard question without good answers right now.
LatencyTOP is a Linux* tool for software developers (both kernel and userspace), aimed at identifying where in the system latency is happening, and what kind of operation/action is causing the latency to happen so that the code can be changed to avoid the worst latency hiccups.
它是Intel贡献的另外一个性能查看器,还有一个是powertop,都是很不错的工具.
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