Lighttpd

the first request (whic is not "not modified") loads really fast, but a second request by pressing F5, takes so much time to load

# connecting to proxy which is an apache
connect(6, {sa_family=AF_INET, sin_port=htons(81), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
time(NULL)                              = 1207455529
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLOUT, revents=POLLOUT}, {fd=3, events=POLLHUP}], 3, 1000) = 1
getsockopt(6, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
time(NULL)                              = 1207455529
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN|POLLOUT, revents=POLLOUT}, {fd=3, events=POLLHUP}], 3, 1000) = 1
# forward request to backend
writev(6, [{"GET /~alecs/fun/xiaoming.txt HTTP/1.1\r\nX-Forwarded-For: 222.125.201.236\r\nX-Host: localhost:82\r\nX-Forwarded-Proto: http\r\nAccept: */*\r\nAccept-Language: zh-cn,en-us;q=0.7,zh-tw;q=0.3\r\nUA-CPU: x86\r\nAccept-Encoding: gzip, deflate\r\nIf-Modified-Since: Thu, 03 Apr 2008 04:55:24 GMT\r\nIf-None-Match: \"4abd1-334-cf324700\"\r\nUser-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)\r\nHost: localhost:82\r\nCookie: __utma=230486913.63839591.1193234124.1206885823.1207400810.7; __utmz=230486913.1193234124.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none)\r\n\r\n", 582}], 1) = 582
time(NULL)                              = 1207455529
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN, revents=POLLIN}, {fd=3, events=POLLHUP}], 3, 1000) = 1
# got response
read(6, "HTTP/1.1 304 Not Modified\r\nDate: Sun, 06 Apr 2008 04:18:49 GMT\r\nServer: Apache/2.2.6 (Debian) DAV/2 SVN/1.4.4\r\nETag: \"4abd1-334-cf324700\"\r\n\r\n", 16384) = 141
# but not sending to client, keep waiting
time(NULL)                              = 1207455529
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455530
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455531
time(NULL)                              = 1207455531
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455532
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455533
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455534
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455535
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455536
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455537
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455538
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455539
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455540
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455541
time(NULL)                              = 1207455541
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455542
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=-1}], 3, 1000) = 0
time(NULL)                              = 1207455543
poll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN, revents=POLLIN}, {fd=-1}], 3, 1000) = 1
# backend close
read(6, "", 16384)                      = 0
close(6)                                = 0
setsockopt(3, SOL_TCP, TCP_CORK, [1], 4) = 0
# response to client
writev(3, [{"HTTP/1.1 304 Not Modified\r\nDate: Sun, 06 Apr 2008 04:18:49 GMT\r\nServer: Apache/2.2.6 (Debian) DAV/2 SVN/1.4.4\r\nETag: \"4abd1-334-cf324700\"\r\nTransfer-Encoding: chunked\r\n\r\n", 169}, {"0\r\n\r\n", 5}], 2) = 174
setsockopt(3, SOL_TCP, TCP_CORK, [0], 4) = 0
open("/etc/localtime", O_RDONLY)        = 6
fstat64(6, {st_mode=S_IFREG|0644, st_size=405, ...}) = 0
fstat64(6, {st_mode=S_IFREG|0644, st_size=405, ...}) = 0