我有一个 LAMP 系统，其中安装了 CentOS 6.4、Apache 2.2.15、MySQL 5.5.32 和 PHP 5.3.26，以及 APC 3.1.10，并在具有 4 个 CPU 和 6 GB RAM 的虚拟机上使用 Drupal CMS（https）。
我的问题是 apache 进程的 CPU 使用率，如果我执行一个包含 10 个并发请求的网页爬虫，该使用率将高达 100%。我该怎么做才能降低 CPU 使用率？有什么想法吗？以下是我的top结果和带有页面的配置文件mod_status server-status：
top - 20:37:23 up 14 days, 22:52, 2 users, load average: 8.54, 6.45, 3.22
Tasks: 180 total, 8 running, 171 sleeping, 0 stopped, 1 zombie
Cpu(s): 93.5%us, 6.2%sy, 0.0%ni, 0.0%id, 0.1%wa, 0.0%hi, 0.2%si, 0.0%st
Mem: 8061508k total, 7634052k used, 427456k free, 146132k buffers
Swap: 8208376k total, 35116k used, 8173260k free, 5019896k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13155 apache 20 0 472m 95m 41m R 69.8 1.2 0:04.75 httpd
13144 apache 20 0 467m 88m 40m R 61.8 1.1 0:03.49 httpd
13141 apache 20 0 477m 97m 39m R 52.9 1.2 0:06.69 httpd
13162 apache 20 0 449m 71m 41m R 51.5 0.9 0:04.53 httpd
13145 apache 20 0 473m 93m 39m R 30.6 1.2 0:02.13 httpd
13136 apache 20 0 477m 98m 40m R 28.9 1.3 0:04.93 httpd
13158 apache 20 0 459m 79m 38m S 28.9 1.0 0:00.87 httpd
13160 apache 20 0 467m 84m 36m R 24.9 1.1 0:00.75 httpd
3496 mysql 20 0 2454m 374m 5072 S 19.6 4.8 31:10.75 mysqld
13120 apache 20 0 460m 81m 40m S 15.3 1.0 0:05.63 httpd
13148 apache 20 0 462m 82m 39m R 12.0 1.1 0:01.79 httpd
我在我的中使用它httpd.conf：
Timeout 60
KeepAlive On
MaxKeepAliveRequests 128
KeepAliveTimeout 10
<IfModule prefork.c>
StartServers 16
MinSpareServers 10
MaxSpareServers 40
ServerLimit 256
MaxClients 256
MaxRequestsPerChild 4000
</IfModule>
这是我 MySQL 中的内容my.cnf（其他为默认）：
max_allowed_packet = 64M
query_cache_size = 128M
query_cache_type = 1
query_cache_limit= 1M
slow-query-log-file=/var/log/mysqld/log-slow-queries.log // nothing logged -> no slow queries
table_cache = 1K
table_definition_cache = 4K
open_files_limit = 3K
thread_cache_size = 3
mod_status如果服务器无事可做，则显示以下内容：
Parent Server Generation: 0
Server uptime: 23 seconds
Total accesses: 10 - Total Traffic: 49 kB
CPU Usage: u.04 s0 cu0 cs0 - .174% CPU load
.435 requests/sec - 2181 B/second - 5017 B/request
1 requests currently being processed, 15 idle workers
W_______________................................................
................................................................
................................................................
................................................................
Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process
Srv PID Acc M CPU SS Req Conn Child Slot Client VHost Request
0-0 14223 10/10/10 W 0.04 0 0 49.1 0.05 0.05 IP www.test.com GET /server-status HTTP/1.1
使用一个网站爬虫（约10个并发请求）：
Server uptime: 5 minutes 46 seconds
Total accesses: 1883 - Total Traffic: 65.5 MB
CPU Usage: u365.13 s17.79 cu0 cs0 - 111% CPU load
5.44 requests/sec - 193.8 kB/second - 35.6 kB/request
15 requests currently being processed, 10 idle workers
WWWW_WWKW___W_W__WW__K_WW.......................................
................................................................
................................................................
................................................................
Srv PID Acc M CPU SS Req Conn Child Slot Client VHost Request
0-0 14223 90/207/207 W 2.07 0 0 902.0 1.61 1.61 IP www.test.com GET /server-status HTTP/1.1
1-0 14224 11/70/70 W 18.87 47 0 279.7 0.84 0.84 IP www.test.com GET /site1
2-0 14225 0/19/19 W 9.66 1 0 0.0 0.95 0.95 IP www.test.com GET /site2
3-0 14226 1/84/84 W 13.94 36 0 0.0 2.14 2.14 IP www.test.com GET /site3.pdf
4-0 14227 0/153/153 _ 27.46 4 81 0.0 3.56 3.56 IP www.test.com GET /site4pdf
5-0 14228 12/78/78 W 17.59 1 0 275.8 2.67 2.67 IP www.test.com GET /site5.pdf
6-0 14229 10/90/90 W 14.62 0 0 611.4 3.85 3.85 IP www.test.com GET /site6
7-0 14230 4/53/53 K 34.12 0 141 9 81.9 2.48 IP www.test.com GET /site7
8-0 14231 1/114/114 W 12.39 27 0 0.0 2.29 2.29 IP www.test.com GET /site8.pdf
9-0 14232 0/106/106 _ 9.68 2 64 0.0 6.33 6.33 IP www.test.com GET /site9
10-0 14233 0/39/39 _ 15.66 5 1376 0.0 2.68 2.68 IP www.test.com GET /site10
11-0 14234 0/36/36 _ 11.31 5 128 0.0 2.78 2.78 IP www.test.com GET /site11
12-0 14235 1/63/63 W 10.58 7 0 70.9 3.59 3.59 IP www.test.com GET /site12.pdf
13-0 14236 0/100/100 _ 22.76 1 20 0.0 2.76 2.76 IP www.test.com GET /site13
14-0 14237 0/63/63 W 4.34 37 0 0.0 0.58 0.58 IP www.test.com GET /site14
15-0 14238 0/12/12 _ 1.75 0 29 0.0 1.85 1.85 IP www.test.com GET /site15
16-0 14283 0/43/43 _ 14.94 1 119 0.0 2.25 2.25 IP www.test.com GET /site16
17-0 14286 8/80/80 W 6.79 0 0 222.7 5.98 5.98 IP www.test.com GET /site17.pdf
18-0 14288 3/111/111 W 21.87 0 0 60.5 2.35 2.35 IP www.test.com GET /site18.pdf
19-0 14289 0/75/75 _ 18.81 5 31 0.0 3.06 3.06 IP www.test.com GET /site19
20-0 14290 0/50/50 _ 16.15 1 259 0.0 2.16 2.16 IP www.test.com GET /site20.pdf
21-0 14292 6/88/88 K 23.71 0 0 32.8 2.79 2.79 IP www.test.com GET /site21
22-0 14293 0/92/92 _ 30.82 1 45 0.0 3.78 3.78 IP www.test.com GET /site22
23-0 14294 11/37/37 W 12.85 27 0 774.2 1.48 1.48 IP www.test.com GET /site23.pdf
24-0 14302 16/20/20 W 10.18 37 0 557.3 0.68 0.68 IP www.test.com GET /site24.pdf
在爬行结束时我已经达到了Srv 46-0。
交换？这是我在爬取完成后做的：
# swapon -s
Filename Type Size Used Priority
/dev/am-1 partition 8208376 35172 -1
# free
total used free shared buffers cached
Mem: 8061508 7287776 773732 0 147220 4806004
-/+ buffers/cache: 2334552 5726956
Swap: 8208376 35172 8173204
答案1
从这些内容来看，您似乎正在进行交换。交换非常糟糕，会导致大量 CPU 被消耗在执行 I/O 交换进程中。您可以考虑添加更多内存……或减少启动的 Apache 服务器数量。
答案2
使用新遗物并查看您的应用程序的网络交易。
New Relic 现在也包含 Drupal 特定的工具（模块、挂钩、视图）。
抱歉，这听起来像是商业广告，但如果您运行的是 Drupal，它提供的丰富信息确实不费吹灰之力。我与 New Relic 没有任何关系，只是一名满意的客户。
如果你想用困难的方式分析你的代码（例如 oprofile）
高血压
附言
您可以将thread_cache_size增加到更合理的数字（例如32），但我怀疑它是否会产生显著的差异。