[squid-users] NONE/501 when rotate or reconfigure

One of my server is running squid-3.1.19 as a reverse proxy,when /path/to/sbin/squid -k rotate or reconfigure,some log display on access.log,and it last over a few minitues,how to avoid it, thanks.
61.x.x.x - - 2012-04-18 02:23:22 "GET NONE://xx.xx.com:80/jiechangai/zz/288268.html HTTP/0.0" 501 1004 "-" "-" NONE:NONE
117.x.x.x - - 2012-04-18 02:23:23 "GET NONE://xx.xx.com:80/file/ad//0000/04fa/hdpi.xml HTTP/0.0" 501 2644 "-" "-" NONE:NONE
61.x.x.x - - 2012-04-18 02:23:26 "GET NONE://xx.xx.com:80/filmlist/1_18.html HTTP/0.0" 501 981 "-" "-" NONE:NONE
120.x.x.x - - 2012-04-18 02:23:26 "GET NONE://xx.xx.com:80/skins/default2/images/search.gif HTTP/0.0" 501 1008 "-" "-" NONE:NONE
120.x.x.x - - 2012-04-18 02:23:26 "GET NONE://xx.xx.com:80/skins/default2/images/menus.gif HTTP/0.0" 501 1006 "-" "-" NONE:NONE
61.x.x.x - - 2012-04-18 02:23:27 "GET NONE://xx.xx.com:80/space/tzmore.asp?id=37268 HTTP/0.0" 501 996 "-" "-" NONE:NONE
120.x.x.x - - 2012-04-18 02:23:28 "GET NONE://xx.xx.com:80/js/player/loading.html HTTP/0.0" 501 988 "-" "-" NONE:NONE
120.x.x.x - - 2012-04-18 02:23:28 "GET NONE://xx.xx.com:80/skins/default2/images/title.gif HTTP/0.0" 501 1006 "-" "-" NONE:NONE
60.x.x.x - - 2012-04-18 02:23:28 "GET NONE://xx.xx.com:80/ad/bdyy.html HTTP/0.0" 501 967 "-" "-" NONE:NONE
60.x.x.x - - 2012-04-18 02:23:32 "GET NONE://xx.xx.com:80/ad/200.js HTTP/0.0" 501 961 "-" "-" NONE:NONE
122.x.x.x - - 2012-04-18 02:23:39 "GET NONE://xx.xx.com:80/ad/view-tj.js HTTP/0.0" 501 972 "-" "-" NONE:NONE
61.x.x.x - - 2012-04-18 02:23:44 "GET NONE://xx.xx.com:80/html/2007/10/3616.html HTTP/0.0" 501 3288 "-" "-" NONE:NONE
61.x.x.x - - 2012-04-18 02:24:07 "GET NONE://xx.xx.com:80/list_211/0-0_0-0/1-0-0-0-39.html HTTP/0.0" 501 1010 "-" "-" NONE:NONE
114.x.x.x - - 2012-04-18 02:24:23 "GET NONE://xx.xx.com.cn:80/mainweb/img/color/qianzhong.png HTTP/0.0" 501 1023 "-" "-" NONE:NONE

2012-04-18
Received on Tue Apr 17 2012 - 19:38:06 MDT