深入理解perf報(bào)告中的swapper進(jìn)程

1、深入理解perf報(bào)告中的swapper進(jìn)程深化理解perf報(bào)告中的swapper進(jìn)程一、前言1、在perf監(jiān)控進(jìn)程的系統(tǒng)調(diào)用時(shí)，會浮現(xiàn)大量swapper進(jìn)程2、官方描述該進(jìn)程是當(dāng)cpu上沒有其他任務(wù)運(yùn)行時(shí)，就會執(zhí)行swapper。換句話說swapper意味著cpu啥事也沒干，跑去歇息去了3、本文來觀看一下swapper在cpu上的表現(xiàn) 二、環(huán)境預(yù)備組件版本osubuntu 16.04.4 ltssystemtapversion 4.2/0.165, commit release-4.1-41-g9cde541d4464 三、預(yù)備腳本祭出我們強(qiáng)有力的工具systemtap，這里需要注重的是，sy

2、stemtap各版本之間有一定的差異，rootwilson-ubuntu:/opt/stap stap -vsystemtap translator/driver (version 4.2/0.165, commit release-4.1-41-g9cde541d4464)copyright (c) 2005-2019 red hat, inc. and othersthis is free software; see the source for copying conditions.tested kernel versions: 2.6.18 . 5.1-rc2enabled featu

3、res: python3 nls確定好版本之后，編寫一個(gè)腳本，主要用到probe:scheduler.cpu_off，/systemtap/tapsets/api-scheduler-cpu-off.html腳本如下：probe scheduler.cpu_off printf("%20s (%5d) %5s %20s (%5d) , is idle:%d n ", task_execname(task_prev),task_pid(task_prev),"=",task_execname(task_next),

4、task_pid(task_next),idle) 腳本十分容易，scheduler.cpu_off主要描述了進(jìn)程離開cpu的狀態(tài)：task_prev：即將離開cpu的進(jìn)程task_next：即將進(jìn)入cpu的進(jìn)程idle：cpu是否處于空閑，這個(gè)變量就是我們關(guān)注的重點(diǎn)，假如idle為1，那就證實(shí)cpu并沒有運(yùn)行任務(wù)四、運(yùn)行腳本因?yàn)閿?shù)據(jù)量太大，我們篩選一部分：rootwilson-ubuntu:/opt/stap stap switch.stp. swapper/0 ( 0) = stapio (29159) , is idle:1 stapio (29159) = swapper/0 ( 0)

5、 , is idle:0 swapper/0 ( 0) = rcu_sched ( 7) , is idle:1 rcu_sched ( 7) = swapper/0 ( 0) , is idle:0 swapper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is idle:0 swapper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is id

6、le:0 swapper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is idle:0 swapper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is idle:0 swapper/0 ( 0) = rcu_sched ( 7) , is idle:1 rcu_sched ( 7) = swapper/0 ( 0) , is idle:0 swa

7、pper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is idle:0 swapper/2 ( 0) = irq/31-iwlwifi ( 542) , is idle:1 irq/31-iwlwifi ( 542) = swapper/2 ( 0) , is idle:0 swapper/0 ( 0) = rcu_sched ( 7) , is idle:1 swapper/1 ( 0) = stapio (29159) , is idle:1 .1、因?yàn)槭?核的cpu，所以有4個(gè)swapper，swapper/n2、swapper的進(jìn)程號是0，在系統(tǒng)初始化時(shí)創(chuàng)建init進(jìn)程，之后它就成了一個(gè)最低優(yōu)先級的空閑任務(wù)3、當(dāng)swapper浮現(xiàn)在左邊的時(shí)候（即將離開cpu的進(jìn)程），對應(yīng)最后一個(gè)字段