10个用户1个并发=100个用户1个并发 相等吗？

如题。

还有就是 这个-n 后面的请求数 是指用户数吗？
是指：10个用户 请求服务器时， 可能有1个并发 或1-10个并发，或者可能0个并发？

ab -n 10 -c 1 http://localhost/a.php
ab -n 100 -c 1 http://localhost/a.php
ab -n 1000 -c 1 http://localhost/a.php

回复讨论(解决方案)

Options are:
-n requests Number of requests to perform
-c concurrency Number of multiple requests to make
-t timelimit Seconds to max. wait for responses
-b windowsize Size of TCP send/receive buffer, in bytes
-p postfile File containing data to POST. Remember also to set -T
-T content-type Content-type header for POSTing, eg.
'application/x-www-form-urlencoded'
Default is 'text/plain'
-v verbosity How much troubleshooting info to print
-w Print out results in HTML tables
-i Use HEAD instead of GET
-x attributes String to insert as table attributes
-y attributes String to insert as tr attributes
-z attributes String to insert as td or th attributes
-C attribute Add cookie, eg. 'Apache=1234. (repeatable)
-H attribute Add Arbitrary header line, eg. 'Accept-Encoding: gzip'
Inserted after all normal header lines. (repeatable)
-A attribute Add Basic WWW Authentication, the attributes
are a colon separated username and password.
-P attribute Add Basic Proxy Authentication, the attributes
are a colon separated username and password.
-X proxy:port Proxyserver and port number to use
-V Print version number and exit
-k Use HTTP KeepAlive feature
-d Do not show percentiles served table.
-S Do not show confidence estimators and warnings.
-g filename Output collected data to gnuplot format file.
-e filename Output CSV file with percentages served
-r Don't exit on socket receive errors.
-h Display usage information (this message)

借助在线翻译，不难看懂吧？
你
ab -n 10 -c 1 http://localhost/a.php
表示 10 个请求，并发数为 1