perf

I tried out linux' perf utility today and am having trouble in interpreting its results. I'm used to valgrind's callgrind which is of course a totally different approach to the sampling based method of perf. What I did: perf record -g -p $(pidof someapp) perf report -g -n Now I see something like this: + 16.92% kdevelop libsqlite3.so.0.8.6 [.] 0x3fe57 ↑ + 10.61% kdevelop libQtGui.so.4.7.3 [.] 0x81e344 ▮ + 7.09% kdevelop libc-2.14.so [.] 0x85804 ▒ + 4.96% kdevelop libQtGui.so.4.7.3 [.] 0x265b69 ▒ + 3.50% kdevelop libQtCore.so.4.7.3 [.] 0x18608d ▒ + 2.68% kdevelop libc-2.14.so [.] memcpy ▒ + 1

　　java 语言有个神奇的地方，那就是你时不时会去关注下内存。（当然了，任何牛逼的同学都应该关注内存） 　　今天我们就来这么场景吧：某应用运行了一段时间后，ecs监控报警了，内存比较高了，怎么办？随着时间的推移，发现内存越来越高（但是又不会打到100%），怎么办？ 　　凡事讲究证据，报警说内存紧张就紧张吗，还得自己去验一下。 如何确认内存问题？这太重要了！ 以下是几种查看内存问题的方法：（爱信不信啊） 1. top 等查看系统内存概况 　　top：内存去，按M按照内存大小排序，立马看到罪魁祸首。具体命令请参考网上资料。 　　top简要使用方法如下： 使用格式： top [-] [d] [p] [q] [c] [C] [S] [s] [n] 参数说明： d：指定每两次屏幕信息刷新之间的时间间隔。当然用户可以使用s交互命令来改变之。 p:通过指定监控进程ID来仅仅监控某个进程的状态。 q:该选项将使top没有任何延迟的进行刷新。如果调用程序有超级用户权限，那么top将以尽可能高的优先级运行。 S：指定累计模式。 s：使top命令在安全模式中运行。这将去除交互命令所带来的潜在危险。 i：使top不显示任何闲置或者僵死进程。 c:显示整个命令行而不只是显示命令名。 常用命令说明： Ctrl+L：擦除并且重写屏幕 K：终止一个进程。系统将提示用户输入需要终止的进程PID

I was playing with the code in this answer , slightly modifying it: BITS 64 GLOBAL _start SECTION .text _start: mov ecx, 1000000 .loop: ;T is a symbol defined with the CLI (-DT=...) TIMES T imul eax, eax lfence TIMES T imul edx, edx dec ecx jnz .loop mov eax, 60 ;sys_exit xor edi, edi syscall Without the lfence I the results I get are consistent with the static analysis in that answer. When I introduce a single lfence I'd expect the CPU to execute the imul edx, edx sequence of the k-th iteration in parallel with the imul eax, eax sequence of the next ( k+1-th ) iteration. Something like this

I try to do some nodejs profiling using Linux perf_events as described by Brendan Gregg here . Workflow is following: run node >0.11.13 with --perf-basic-prof , which creates /tmp/perf-(PID).map file where JavaScript symbol mapping are written. Capture stacks using perf record -F 99 -p `pgrep -n node` -g -- sleep 30 Fold stacks using stackcollapse-perf.pl script from this repository Generate svg flame graph using flamegraph.pl script I get following result (which look really nice at the beginning): Problem is that there are a lot of [unknown] elements, which I suppose should be my nodejs