订购并设置了新的 Web 服务器（64 位、4 vCores、6GB RAM、Ubuntu 14.04）后，使用 Apache 2.4.7（和 PHP7 fpm）作为事件 MPM，但在流量高峰期，Apache 崩溃了。错误日志中充满了数百条条目（即使在流量较少的时段也是如此），如下所示：
[Thu Jul 21 17:51:16.633617 2016] [mpm_event:crit] [pid 9290:tid 139705492948732] (22)Invalid argument: ap_queue_pop failed
[Thu Jul 21 17:51:16.633622 2016] [mpm_event:crit] [pid 9290:tid 139705492948732] (22)Invalid argument: ap_queue_pop failed
[Thu Jul 21 17:51:16.633627 2016] [mpm_event:crit] [pid 9290:tid 139705492948732] (22)Invalid argument: ap_queue_pop failed
[Thu Jul 21 17:51:18.632095 2016] [mpm_event:alert] [pid 9313:tid 139705857640190] (11)Resource temporarily unavailable: apr_thread_create: unable to create worker thread
[Thu Jul 21 17:51:19.632842 2016] [mpm_event:alert] [pid 9337:tid 139705857640190] (11)Resource temporarily unavailable: apr_thread_create: unable to create worker thread
我已经通过以下方式默认设置了较高的系统限制ulimit -a：
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 1546681
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 10240
cpu time (seconds, -t) unlimited
max user processes (-u) 1546681
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
这来自 Mozilla 的博客文章也没有帮助，因为我的限额已经远远高于他们建议的限额。我还读了增加privvmpages价值但它也很高：
$ cat /proc/user_beancounters
Version: 2.5
uid resource held maxheld barrier limit failcnt
130922: kmemsize 173862701 175349760 9223372036854775807 9223372036854775807 0
lockedpages 0 0 1572864 1572864 0
privvmpages 3327626 3330707 3670016 3670016 31705
shmpages 92638 92638 9223372036854775807 9223372036854775807 0
dummy 0 0 9223372036854775807 9223372036854775807 0
numproc 279 363 850 850 0
physpages 356751 363453 0 1572864 0
vmguarpages 0 0 1835008 1835008 0
oomguarpages 121370 121370 1572864 1572864 0
numtcpsock 69 72 9223372036854775807 9223372036854775807 0
numflock 11 12 9223372036854775807 9223372036854775807 0
numpty 2 2 9223372036854775807 9223372036854775807 0
numsiginfo 0 63 9223372036854775807 9223372036854775807 0
tcpsndbuf 1368640 1445072 9223372036854775807 9223372036854775807 0
tcprcvbuf 1938112 1987264 9223372036854775807 9223372036854775807 0
othersockbuf 233512 241968 9223372036854775807 9223372036854775807 0
dgramrcvbuf 0 0 9223372036854775807 9223372036854775807 0
numothersock 148 150 9223372036854775807 9223372036854775807 0
dcachesize 61545508 61876256 9223372036854775807 9223372036854775807 0
numfile 2133 2280 9223372036854775807 9223372036854775807 0
dummy 0 0 9223372036854775807 9223372036854775807 0
dummy 0 0 9223372036854775807 9223372036854775807 0
dummy 0 0 9223372036854775807 9223372036854775807 0
numiptent 338 338 9223372036854775807 9223372036854775807 0
$ free -m
total used free shared buffers cached
Mem: 6144 1823 4320 361 0 1553
-/+ buffers/cache: 270 5873
Swap: 1024 0 1024
该网站一天总共收到 500,000 个请求，但之前它运行在更旧（软件/硬件）和更小的服务器上（资源只有一半），没有任何（资源）问题。我的 mpm-event 设置：
<IfModule mpm_event_module>
StartServers 5
ServerLimit 32
MinSpareThreads 60
MaxSpareThreads 200
ThreadLimit 64
ThreadsPerChild 25
MaxRequestWorkers 800
MaxConnectionsPerChild 20000
</IfModule>
负载通常约为 0.05，并且 RAM 的使用率通常不超过 10%。知道我做错了什么吗？
（小注：这是我利用业余时间开发的一项人们免费使用的服务。）