基于busybox的bootchart分析

一、Bootchart简介

Bootchart官网http://www.bootchart.org，已经很久没有更新了。

Bootchart的目的是将启动阶段的性能可视化（Boot Process Performance Visualization）。具体做法是在启动阶段通过采样/proc文件系统来搜集启动阶段的信息（如CPU负载，进程信息，磁盘访问等），然后通过另外的工具将搜集到的数据以可视化的方式进行输出。

因此，bootchart分为两个部分：

• 采样程序bootchartd，系统启动后的第一个进程，采样并搜集启动过程中的/proc数据，启动完成后将采样数据压缩存放到/var/log/bootchart/bootlog.tgz文件中
• 外部工具pybootchartgui，处理bootlog.tgz文件，输出为图片
  
  • 对于PC，系统会在启动完成后自动生成bootlog.png文件
  • 对于嵌入式系统，需要将bootlog.tgz导出到PC上进行处理

下图是一个嵌入式系统上的bootchart输出的示例图片：

我在虚拟机上安装bootchart并抓取了启动过程数据，点这里查看Ubuntu 12.04启动后生成的图片。

在bootchart生成的图像中，可以清楚的看到启动过程中CPU负载、磁盘吞吐和各进程实时的情况。

二、Bootchart配置

Busybox从v1.17版本开始引入bootchartd。
相比PC，嵌入式系统没有完备的Bootchart工具，启动过程中采样的数据需要导出在PC上进行处理。

Busybox上通过执行make menuconfig配置bootchartd，具体位置如下：

ygu@ubuntu:/opt/work/busybox$ make menuconfig    Busybox Settings   --->--- Applets    ...    Init Utilities   --->        [*] bootchartd        [*]   Compatible, bloated header        [*]   Support bootchartd.conf    ...

默认设置打开所有bootchartd设置：

设置总共有3项：

• 选项[*] bootchartd，设置[BOOTCHARTD =y]，是bootchart功能开关
• 选项[*] Compatible, bloated header，设置[FEATURE_BOOTCHARTD_BLOATED_HEADER =y]，设置后bootchartd会生成一个包含类似如下信息的header文件：

version = 0.8title = Boot chart for (none) (Thu Jan  1 00:01:05 UTC 1970)system.uname = Linux 3.3.8-4.0 #6 SMP Tue Nov 29 14:23:14 CST 2016 mipssystem.kernel.options = ubiroot init=/sbin/bootchartd ubi.mtd=rootfs rootfstype=ubifs root=ubi0:rootfs

• 选项[*] Support bootchartd.conf，设置[FEATURE_BOOTCHARTD_CONFIG_FILE =y]，设置后bootchartd启动时会尝试读取并解析配置文件/etc/bootchartd.conf，配置文件的格式类似如下：

## supported options:## Sampling period (in seconds)SAMPLE_PERIOD=0.2## not yet supported:## tmpfs size# (32 MB should suffice for ~20 minutes worth of log data, but YMMV)TMPFS_SIZE=32m# Whether to enable and store BSD process accounting information.  The# kernel needs to be configured to enable v3 accounting# (CONFIG_BSD_PROCESS_ACCT_V3). accton from the GNU accounting utilities# is also required.PROCESS_ACCOUNTING="no"# Tarball for the various boot log filesBOOTLOG_DEST=/var/log/bootchart.tgz# Whether to automatically stop logging as the boot process completes.# The logger will look for known processes that indicate bootup completion# at a specific runlevel (e.g. gdm-binary, mingetty, etc.).AUTO_STOP_LOGGER="yes"# Whether to automatically generate the boot chart once the boot logger# completes.  The boot chart will be generated in $AUTO_RENDER_DIR.# Note that the bootchart package must be installed.AUTO_RENDER="no"

从busybox中bootchartd实现的代码来看，仅支持SAMPLE_PERIOD和SAMPLE_PERIOD两个选项。当然，也可以不用设置/etc/bootchartd.conf而使用代码中默认的设置。

三、Bootchart运行

bootchart的帮助信息：

Usage: bootchartd start [PROG ARGS]|stop|initOptions:start: start background logging; with PROG, run PROG, then kill logging with USR1stop: send USR1 to all bootchartd processesinit: start background logging; stop when getty/xdm is seen (for init scripts)Under PID 1: start background logging, then execute $bootchart_init, /init, /sbin/initThis makes it possible to start bootchartd even before init by booting kernel with:init=/sbin/bootchartd bootchart_init=/path/to/regular/init

从帮助信息可见bootchartd有两个用途：

• linux启动时运行用于采样linux启动过程中的各项数据
• 启动完成后运行，用于监测系统或指定应用程序

1. linux启动时运行

这是使用最多的方式，在linux启动的命令行中指定/sbin/bootchartd为init进程。

• 带initramfs的系统，需要在命令行指定rdinit
rdinit=/sbin/bootchartd

• 非initramfs的系统，需要在命令行指定init
init=/sbin/bootchartd

linux启动中，会用/sbin/bootchartd创建第一个进程，然后在bootchartd中再fork一个真正的init进程。如果在启动的同时通过命令行指定了bootchart_init参数，则用这个参数指定的程序用于fork生成的init进程，否则依次使用默认的/init或/sbin/init作为init进程。如：

init=/sbin/bootchartd bootchart_init=/path/to/regular/init

以下是我在博通7583参考平台上使用带文件系统的kernel启动的log:

CFE> CFE> boot -z -elf 192.168.1.95:7584a0/vmlinuz-initrd-7584a0 'rdinit=/sbin/bootchartd quiet'Loader:elf Filesys:tftp Dev:eth0 File:192.168.1.95:7584a0/vmlinuz-initrd-7584a0 Options:rdinit=/sbin/bootchartd quietLoading: 0x80001000/11957248 0x80b68400/110224 Entry address is 0x8045f360Closing network.Starting program at 0x8045f360Linux version 3.3.8-4.0 (ygu@fs-ygu) (gcc version 4.5.4 (Broadcom stbgcc-4.5.4-2.9) ) #5 SMP Tue Nov 29 14:23:04 CST 2016Fetching vars from bootloader... found 14 vars.Options: moca=0 sata=1 pcie=0 usb=1Using 512 MB + 0 MB RAM (from CFE)bootconsole [early0] enabledCPU revision is: 0002a065 (Broadcom BMIPS4380)FPU revision is: 00130001Determined physical RAM map: memory: 10000000 @ 00000000 (usable) memory: 10000000 @ 20000000 (usable)No PHY detected, not registering interface:1starting pid 429, tty '': '/etc/init.d/rcS'Mounting virtual filesystemsStarting mdev* WARNING: THIS STB CONTAINS GPLv3 SOFTWARE* GPLv3 programs must be removed in order to enable security.* See: http://www.gnu.org/licenses/gpl-faq.html#TivoizationConfiguring eth0 interfaceConfiguring lo interfaceStarting network servicesstarting pid 459, tty '': '/bin/cttyhack /bin/sh -l'# # shell-init: error retrieving current directory: getcwd: cannot access parent directories: Success## ls -lh /var/log/            -rw-r--r--    1 root     root       28.9K Jan  1 00:01 bootlog.tgz#

可以看到，系统启动完成后会在/var/log目录下生成bootlog.tgz文件（PC上采样的数据文件位于/var/log/bootchartd/目录下）。将文件/var/log/bootlog.tgz复制到PC上备用。

在主机上安装bootchart工具，安装的同时还会安装pybootchartgui用于将采集的数据转换为图片。

ygu@ubuntu:~$ sudo apt-get install bootchart[sudo] password for ygu: Reading package lists... DoneBuilding dependency tree       Reading state information... DoneThe following NEW packages will be installed:  bootchart0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.Need to get 0 B/11.0 kB of archives.After this operation, 127 kB of additional disk space will be used.Selecting previously unselected package bootchart.(Reading database ... 170788 files and directories currently installed.)Unpacking bootchart (from .../bootchart_0.90.2-8ubuntu1_i386.deb) ...Processing triggers for ureadahead ...Setting up bootchart (0.90.2-8ubuntu1) ...update-initramfs: Generating /boot/initrd.img-3.13.0-32-genericygu@ubuntu:~$ scp ygu@192.168.1.95:/opt/bootchartd/bootlog.tgz work/bootchartbootlog.tgz                                   100%   29KB  29.3KB/s   00:00    ygu@ubuntu:~$ cd work/bootchart

使用pybootchartgui处理bootlog.tgz：

ygu@ubuntu:~/work/bootchart$ ls -lhtotal 32K-rw-r--r-- 1 ygu ygu 30K Dec  1 10:28 bootlog.tgzygu@ubuntu:~/work/bootchart$ ygu@ubuntu:~/work/bootchart$ pybootchartgui bootlog.tgz parsing 'bootlog.tgz'parsing 'header'parsing 'proc_diskstats.log'parsing 'proc_ps.log'warning: no parent for pid '2' with ppid '0'parsing 'proc_stat.log'merged 0 logger processespruned 29 process, 0 exploders, 0 threads, and 0 runsFalseTraceback (most recent call last):  File "/usr/bin/pybootchartgui", line 23, in <module>    sys.exit(main())  File "/usr/lib/pymodules/python2.7/pybootchartgui/main.py", line 137, in main    render()  File "/usr/lib/pymodules/python2.7/pybootchartgui/main.py", line 128, in render    batch.render(writer, res, options, filename)  File "/usr/lib/pymodules/python2.7/pybootchartgui/batch.py", line 41, in render    draw.render(ctx, options, *res)  File "/usr/lib/pymodules/python2.7/pybootchartgui/draw.py", line 256, in render    curr_y = draw_header(ctx, headers, off_x, duration)  File "/usr/lib/pymodules/python2.7/pybootchartgui/draw.py", line 340, in draw_header    txt = headertitle + ': ' + mangle(headers.get(headerkey))TypeError: cannot concatenate 'str' and 'NoneType' objectsygu@ubuntu:~/work/bootchart$ 

如上，由于Ubuntu版本的pybootchartgui不能解析busybox上的bootchart数据，所以这里出现了错误，需要用另外一个版本bootchart2的工具来处理。

用git下载bootchart2后需要执行make后才能使用pybootchartgui：

ygu@ubuntu:~/work/bootchart$ git clone https://github.com/xrmx/bootchart.gitCloning into 'bootchart'...remote: Counting objects: 2560, done.remote: Total 2560 (delta 0), reused 0 (delta 0), pack-reused 2560Receiving objects: 100% (2560/2560), 1.79 MiB | 228 KiB/s, done.Resolving deltas: 100% (1600/1600), done.ygu@ubuntu:~/work/bootchart$ cd bootchart/ygu@ubuntu:~/work/bootchart/bootchart$ makecc -g -Wall -O0  -pthread \        -DEARLY_PREFIX='""' \        -DLIBDIR='"/lib"' \        -DPKGLIBDIR='"/lib/bootchart"' \        -DPROGRAM_PREFIX='""' \        -DPROGRAM_SUFFIX='""' \        -DVERSION='"0.14.8"' \         \        -c collector/collector.c -o collector/collector.o...cc -g -Wall -O0  -pthread -Icollector -o bootchart-collector collector/collector.o collector/output.o collector/tasks.o collector/tasks-netlink.o collector/dump.osed -s -e "s:@LIBDIR@:/lib:g" -e "s:@PKGLIBDIR@:/lib/bootchart:" -e "s:@PROGRAM_PREFIX@::" -e "s:@PROGRAM_SUFFIX@::" -e "s:@EARLY_PREFIX@::" -e "s:@VER@:0.14.8:" bootchartd.in > bootchartd...sed -s -e "s:@LIBDIR@:/lib:g" -e "s:@PKGLIBDIR@:/lib/bootchart:" -e "s:@PROGRAM_PREFIX@::" -e "s:@PROGRAM_SUFFIX@::" -e "s:@EARLY_PREFIX@::" -e "s:@VER@:0.14.8:" pybootchartgui/main.py.in > pybootchartgui/main.pyygu@ubuntu:~/work/bootchart/bootchart$ 

如果不编译，直接调用pybootchartgui会出现找不到main函数的错误：

ygu@ubuntu:~/work/bootchart$ ./bootchart/pybootchartgui.py bootlog.tgz Traceback (most recent call last):  File "./bootchart/pybootchartgui.py", line 20, in <module>    from pybootchartgui.main import mainImportError: No module named mainygu@ubuntu:~/work/bootchart$ 

编译完成后，再次调用pybootchartgui.py处理bootlog.tgz：

ygu@ubuntu:~/work/bootchart$ ./bootchart/pybootchartgui.py bootlog.tgz parsing 'bootlog.tgz'parsing 'header'parsing 'proc_diskstats.log'parsing 'proc_ps.log'parsing 'proc_stat.log'merged 0 logger processespruned 29 process, 0 exploders, 0 threads, and 0 runsbootchart written to 'bootchart.png'ygu@ubuntu:~/work/bootchart$ ls -lhtotal 96Kdrwxr-xr-x 6 ygu ygu 4.0K Dec  1 10:45 bootchart-rw-rw-r-- 1 ygu ygu  59K Dec  1 10:46 bootchart.png-rw-r--r-- 1 ygu ygu  30K Dec  1 10:28 bootlog.tgzygu@ubuntu:~/work/bootchart$ 

将采集的数据转换为图片bootchart.png了，如下：

由于这里整个linux系统启动的任务比较简单，所以从bootchart.png上可见的任务也较少，这里寄希望于bootchart的结果来进行启动时间优化还是有些难度。

2. 监测系统或应用程序的运行情况

用于监测运行情况时需要给bootchartd指定参数，start参数开始监测，stop参数停止监测。

不过，系统启动后可以监测的手段较多，bootchartd工具并不是最优选择，非本文的介绍重点，暂略。

四、Bootchartd源码分析

busybox\init\bootchartd.c：

• bootchartd_main

/* bootchart的main函数入口 */int bootchartd_main(int argc UNUSED_PARAM, char **argv){    unsigned sample_period_us;    pid_t parent_pid, logger_pid;    smallint cmd;    int process_accounting;    /* bootchart的命令类型 */    enum {        CMD_STOP = 0,   /* STOP命令，用于'bootchart stop' */        CMD_START,      /* START命令， 用于'bootchart start [PROG ARGS]' */        CMD_INIT,       /* INIT命令， 用于'bootchart init'，实际上并没有使用 */        CMD_PID1, /* used to mark pid 1 case */ /* 作为linux启动的init进程时使用，init=/sbin/bootchartd */    };    INIT_G();    /* 获取当前进程pid，init进程的pid为1 */    parent_pid = getpid();    if (argv[1]) { /* 检查bootchartd命令参数 */        cmd = index_in_strings("stop\0""start\0""init\0", argv[1]);        if (cmd < 0)            bb_show_usage();        if (cmd == CMD_STOP) { /* 检查是否是`bootchart stop'命令，如果是，则结束之前所有的'bootchartd'进程，停止监测 */            pid_t *pidList = find_pid_by_name("bootchartd");            while (*pidList != 0) {                if (*pidList != parent_pid)                    kill(*pidList, SIGUSR1);                pidList++;            }            return EXIT_SUCCESS;        }    } else { /* 不带参数时调用 */        if (parent_pid != 1) /* 检查是否是init进程，如果不是init进程，则说明是在命令行调用不带参数的bootchartd，显示usage */            bb_show_usage();        cmd = CMD_PID1;    }    /* Here we are in START, INIT or CMD_PID1 state */    /* 以下读取配置文件，实际上只读取了SAMPLE_PERIOD和PROCESS_ACCOUNTING选项 */    /* 默认采样周期sample_period_us为200ms     * 如果process_accounting=1，用户程序可以让内核将该过程的统计资料情况存到文件里，默认如果process_accounting为0     */    /* Read config file: */    sample_period_us = 200 * 1000;    process_accounting = 0;    if (ENABLE_FEATURE_BOOTCHARTD_CONFIG_FILE) {        char* token[2];        parser_t *parser = config_open2("/etc/bootchartd.conf" + 5, fopen_for_read);        if (!parser)            parser = config_open2("/etc/bootchartd.conf", fopen_for_read);        while (config_read(parser, token, 2, 0, "#=", PARSE_NORMAL & ~PARSE_COLLAPSE)) {            if (strcmp(token[0], "SAMPLE_PERIOD") == 0 && token[1])                sample_period_us = atof(token[1]) * 1000000;            if (strcmp(token[0], "PROCESS_ACCOUNTING") == 0 && token[1]             && (strcmp(token[1], "on") == 0 || strcmp(token[1], "yes") == 0)            ) {                process_accounting = 1;            }        }        config_close(parser);        if ((int)sample_period_us <= 0)            sample_period_us = 1; /* prevent division by 0 */    }    /* 创建用于采样子进程 */    /* Create logger child: */    logger_pid = fork_or_rexec(argv);    if (logger_pid == 0) { /* child */ /* 新创建的采样子进程 */        char *tempdir;        bb_signals(0            + (1 << SIGUSR1)            + (1 << SIGUSR2)            + (1 << SIGTERM)            + (1 << SIGQUIT)            + (1 << SIGINT)            + (1 << SIGHUP)            , record_signo);        /* 就绪后向父进程发送信号 */        if (DO_SIGNAL_SYNC)            /* Inform parent that we are ready */            raise(SIGSTOP);        /* If we are started by kernel, PATH might be unset.         * In order to find "tar", let's set some sane PATH:         */        if (cmd == CMD_PID1 && !getenv("PATH"))            putenv((char*)bb_PATH_root_path);        /* 生成存放采样数据的临时目录 */        tempdir = make_tempdir();        /* 通过`/proc`文件系统进行采样 */        do_logging(sample_period_us, process_accounting);        /* 打包log信息文件，并清理中间生成的tempdir目录 */        finalize(tempdir, cmd == CMD_START ? argv[2] : NULL, process_accounting);        /* 退出子进程 */        return EXIT_SUCCESS;    }    /* parent */    USE_FOR_NOMMU(argv[0][0] &= 0x7f); /* undo fork_or_rexec() damage */    /* 检查子进程发送的信号 */    if (DO_SIGNAL_SYNC) {        /* Wait for logger child to set handlers, then unpause it.         * Otherwise with short-lived PROG (e.g. "bootchartd start true")         * we might send SIGUSR1 before logger sets its handler.         */        waitpid(logger_pid, NULL, WUNTRACED);        kill(logger_pid, SIGCONT);    }    /* 如果当前bootchartd作为init进程，则需要启动真正的init进程 */    if (cmd == CMD_PID1) {        char *bootchart_init = getenv("bootchart_init");        if (bootchart_init) /* 执行参数bootchart_init制定的进程 */            execl(bootchart_init, bootchart_init, NULL);        /* 执行/init作为真正的init进程，成功后不会再返回 */        execl("/init", "init", NULL);        /* 执行/sbin/init作为真正的进程，成功后不会再返回 */        execl("/sbin/init", "init", NULL);        /* 没有找到init进程或执行失败，显示错误信息 */        bb_perror_msg_and_die("can't execute '%s'", "/sbin/init");    }    /* 在命令行运行START命令'bootchart start [PROG ARGS]'的情况，启动需要运行的进程 */    if (cmd == CMD_START && argv[2]) { /* "start PROG ARGS" */        pid_t pid = xvfork();        if (pid == 0) { /* child */            argv += 2;            BB_EXECVP_or_die(argv);        }        /* parent */        waitpid(pid, NULL, 0);        kill(logger_pid, SIGUSR1);    }    return EXIT_SUCCESS;}

• make_tempdir

/* 创建临时的内存文件系统目录 */static char *make_tempdir(void){    char template[] = "/tmp/bootchart.XXXXXX";    char *tempdir = xstrdup(mkdtemp(template)); /* 使用模板/tmp/bootchart.XXXXXX创建一个临时目录，并返回目录名称字符串 */    if (!tempdir) { /* 临时目录创建失败，尝试其他挂载点挂载作为临时目录 */#ifdef __linux__        /* /tmp is not writable (happens when we are used as init).         * Try to mount a tmpfs, them cd and lazily unmount it.         * Since we unmount it at once, we can mount it anywhere.         * Try a few locations which are likely ti exist.         */        static const char dirs[] = "/mnt\0""/tmp\0""/boot\0""/proc\0";        const char *try_dir = dirs;        while (mount("none", try_dir, "tmpfs", MS_SILENT, "size=16m") != 0) {            try_dir += strlen(try_dir) + 1;            if (!try_dir[0])                bb_perror_msg_and_die("can't %smount tmpfs", "");        }        //bb_error_msg("mounted tmpfs on %s", try_dir);        xchdir(try_dir);        if (umount2(try_dir, MNT_DETACH) != 0) {            bb_perror_msg_and_die("can't %smount tmpfs", "un");        }#else        bb_perror_msg_and_die("can't create temporary directory");#endif    } else {        xchdir(tempdir);    }    return tempdir;}

• do_logging

/* 采样/proc文件系统的数据 */static void do_logging(unsigned sample_period_us, int process_accounting){    FILE *proc_stat = xfopen("proc_stat.log", "w");    FILE *proc_diskstats = xfopen("proc_diskstats.log", "w");    //FILE *proc_netdev = xfopen("proc_netdev.log", "w");    FILE *proc_ps = xfopen("proc_ps.log", "w");    int look_for_login_process = (getppid() == 1);    unsigned count = 60*1000*1000 / sample_period_us; /* ~1 minute */    /* 如果process_accounting=1，生成kernel_pacct文件，不清楚为什么要通过acct("kernel_pacct")创建这个文件 */    if (process_accounting) {        close(xopen("kernel_pacct", O_WRONLY | O_CREAT | O_TRUNC));        acct("kernel_pacct");    }    /* 采样 */    while (--count && !bb_got_signal) {        char *p;        int len = open_read_close("/proc/uptime", G.jiffy_line, sizeof(G.jiffy_line)-2);        if (len < 0)            goto wait_more;        /* /proc/uptime has format "NNNNNN.MM NNNNNNN.MM" */        /* we convert it to "NNNNNNMM\n" (using first value) */        G.jiffy_line[len] = '\0';        p = strchr(G.jiffy_line, '.');        if (!p)            goto wait_more;        while (isdigit(*++p))            p[-1] = *p;        p[-1] = '\n';        p[0] = '\0';        /* 采样/proc/stat，输出到proc_stat.log文件 */        dump_file(proc_stat, "/proc/stat");        /* 采样/proc/diskstats，输出到proc_diskstats.log文件 */        dump_file(proc_diskstats, "/proc/diskstats");        //dump_file(proc_netdev, "/proc/net/dev");        /* 采样当前进程活动信息/proc/pid/stat，输出到proc_ps.log文件 */        if (dump_procs(proc_ps, look_for_login_process)) {            /* dump_procs saw a getty or {g,k,x}dm             * stop logging in 2 seconds:             */            if (count > 2*1000*1000 / sample_period_us)                count = 2*1000*1000 / sample_period_us;        }        fflush_all(); wait_more:        usleep(sample_period_us);    }}

• finalize

/* 将采样信息转移到/var/log/bootlogtgz文件并清理临时目录 */static void finalize(char *tempdir, const char *prog, int process_accounting){    //# Stop process accounting if configured    //local pacct=    //[ -e kernel_pacct ] && pacct=kernel_pacct    FILE *header_fp = xfopen("header", "w");    /* 清楚临时文件夹下的kernel_pacct文件     * kernel_pacct在统计开始时创建，统计结束时销毁     * kernel_pacct是用于向系统标记当前是一个统计进程吗？     */    if (process_accounting)        acct(NULL);    /* 如果针对单个进程统计，则往header文件输出采样目标进程的名字 */    if (prog)        fprintf(header_fp, "profile.process = %s\n", prog);    /* 往header文件输出bootchart版本信息 */    fputs("version = "BC_VERSION_STR"\n", header_fp);    /* 设置FEATURE_BOOTCHARTD_BLOATED_HEADER选项后，向header文件输出时间、系统版本、命令行参数等信息 */    if (ENABLE_FEATURE_BOOTCHARTD_BLOATED_HEADER) {        char *hostname;        char *kcmdline;        time_t t;        struct tm tm_time;        /* x2 for possible localized weekday/month names */        char date_buf[sizeof("Mon Jun 21 05:29:03 CEST 2010") * 2];        struct utsname unamebuf;        hostname = safe_gethostname();        time(&t);        localtime_r(&t, &tm_time);        strftime(date_buf, sizeof(date_buf), "%a %b %e %H:%M:%S %Z %Y", &tm_time);        fprintf(header_fp, "title = Boot chart for %s (%s)\n", hostname, date_buf);        if (ENABLE_FEATURE_CLEAN_UP)            free(hostname);        uname(&unamebuf); /* never fails */        /* same as uname -srvm */        fprintf(header_fp, "system.uname = %s %s %s %s\n",                unamebuf.sysname,                unamebuf.release,                unamebuf.version,                unamebuf.machine        );        //system.release = `cat /etc/DISTRO-release`        //system.cpu = `grep '^model name' /proc/cpuinfo | head -1` ($cpucount)        kcmdline = xmalloc_open_read_close("/proc/cmdline", NULL);        /* kcmdline includes trailing "\n" */        fprintf(header_fp, "system.kernel.options = %s", kcmdline);        if (ENABLE_FEATURE_CLEAN_UP)            free(kcmdline);    }    fclose(header_fp);    /* 除kernel_pacct文件外，将临时目录里的所有*.log文件打包到/var/log/bootlog.tgz中 */    /* Package log files */    system(xasprintf("tar -zcf /var/log/bootlog.tgz header %s *.log", process_accounting ? "kernel_pacct" : ""));    /* 清除临时文件目录 */    /* Clean up (if we are not in detached tmpfs) */    if (tempdir) {        unlink("header");        unlink("proc_stat.log");        unlink("proc_diskstats.log");        //unlink("proc_netdev.log");        unlink("proc_ps.log");        if (process_accounting)            unlink("kernel_pacct");        rmdir(tempdir);    }    /* shell-based bootchartd tries to run /usr/bin/bootchart if $AUTO_RENDER=yes:     * /usr/bin/bootchart -o "$AUTO_RENDER_DIR" -f $AUTO_RENDER_FORMAT "$BOOTLOG_DEST"     */}

• dump_file和dump_procs

/* 将filename的内容写入fp文件 */static void dump_file(FILE *fp, const char *filename){    int fd = open(filename, O_RDONLY);    if (fd >= 0) {        fputs(G.jiffy_line, fp);        fflush(fp);        bb_copyfd_eof(fd, fileno(fp));        close(fd);        fputc('\n', fp);    }}/* 获取/proc/pid/stat信息并写入fp文件 */static int dump_procs(FILE *fp, int look_for_login_process){    struct dirent *entry;    DIR *dir = opendir("/proc");    int found_login_process = 0;    fputs(G.jiffy_line, fp);    while ((entry = readdir(dir)) != NULL) {        char name[sizeof("/proc/%u/cmdline") + sizeof(int)*3];        int stat_fd;        unsigned pid = bb_strtou(entry->d_name, NULL, 10);        if (errno)            continue;        /* Android's version reads /proc/PID/cmdline and extracts         * non-truncated process name. Do we want to do that? */         /* 打开/proc/pid/stat文件 */        sprintf(name, "/proc/%u/stat", pid);        stat_fd = open(name, O_RDONLY);        if (stat_fd >= 0) {            char *p;            char stat_line[4*1024];            int rd = safe_read(stat_fd, stat_line, sizeof(stat_line)-2);            close(stat_fd);            if (rd < 0)                continue;            stat_line[rd] = '\0';            p = strchrnul(stat_line, '\n');            *p++ = '\n';            *p = '\0';            fputs(stat_line, fp);            if (!look_for_login_process)                continue;            p = strchr(stat_line, '(');            if (!p)                continue;            p++;            strchrnul(p, ')')[0] = '\0';            /* Is it gdm, kdm or a getty? */            if (((p[0] == 'g' || p[0] == 'k' || p[0] == 'x') && p[1] == 'd' && p[2] == 'm')             || strstr(p, "getty")            ) {                found_login_process = 1;            }        }    }    closedir(dir);    fputc('\n', fp);    return found_login_process;}

五、结论

Bootchart的原理和使用都比较简单，输出也比较直观，通过采样数据并处理生成的图片对整个启动系统形成总览，包括CPU在启动各时间段的负载和磁盘的吞吐情况，也呈现了启动过程中各进程的先后顺序和持续时间。但是在嵌入式系统中，CPU能力普遍不强，Bootchartd本身采样的开销也比较客观，甚至连日志输出的打包也会占用不少时间。另外，由于bootchartd启动上替代了init进程，因此在init进程启动之前的部分，bootchartd也无法反应。