Date: Thu, 5 Nov 1998 23:23:59 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: David Greenman <dg@root.com> Cc: Marc Slemko <marcs@znep.com>, cvs-committers@FreeBSD.ORG Subject: Re: sendfile() Message-ID: <199811060723.XAA01903@apollo.backplane.com> References: <Pine.BSF.4.03.9811052158470.11835-100000@alive.znep.com>
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:sendfile() certainly helped wcarchive, which is a good example of this.
:Zero copy technology helped IBM push numbers on their quad CPU system
:until they actually ran out of bandwidth on the bus with a fair amount of
:...
Heh. Well, I wrote a little program to test the overhead of
sendfile() vs write() in the 100% cached case. The program
makes a tcp connection to another program that just sinks the
data.
Over localhost (with the sink program running on the same
host), it's 9x more efficient to use sendfile(). Over
a 10BaseT Lan (with the sink program running on the
remote host) it's 2x and 2.8x more efficient using
sendfile().
But sendfile() does not apparently handle O_NONBLOCK
descriptors right. This is very important, I think.
Dave? We can't use sendfile() in multi-threaded
select() cores without that. Right now it operates
as if O_NONBLOCK hadn't been specified.
The programs I am using are available at:
http://www.backplane.com/FreeBSD/
-Matt
(send to localhost, sink program running on localhost. Note
user + system time ... sendfile() is 9x more efficient)
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -sendfile -r64 -b4096
0.040u 0.275s 0:02.08 14.9% 5+191k 0+0io 0pf+0w
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -sendfile -r64 -b16384
0.017u 0.279s 0:01.99 14.0% 4+184k 0+0io 0pf+0w
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -sendfile -r64 -b0
0.012u 0.153s 0:01.94 8.2% 6+247k 0+0io 0pf+0w
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -write -r64 -b4096
0.078u 2.746s 0:03.58 78.4% 6+198k 0+0io 0pf+0w
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -write -r64 -b16384
0.029u 2.387s 0:03.26 73.6% 5+209k 0+0io 0pf+0w
# time ./tcpsendfile localhost 5400 /usr/lib/libc_pic.a -write -r64 -b65536
0.029u 2.207s 0:04.18 53.1% 5+206k 0+0io 0pf+0w
(send to host on 10BaseT lan, sink program running on remote.
2x more efficient in this case.)
(Using 16K send/recvpipes via route command)
# time ./tcpsendfile lander 5400 /usr/lib/libc_pic.a -r8 -s -b4096 -write
0.029u 0.519s 0:08.94 5.9% 9+170k 0+0io 0pf+0w
# time ./tcpsendfile lander 5400 /usr/lib/libc_pic.a -r8 -s -b4096 -sendfile
0.017u 0.256s 0:08.90 2.9% 15+284k 0+0io 0pf+0w
(Using 64K send/recvpipes via route command, 2.8x more efficient
in this case).
# time ./tcpsendfile lander 5400 /usr/lib/libc_pic.a -r8 -s -b4096 -write
0.024u 0.538s 0:09.00 6.1% 10+196k 0+0io 0pf+0w
# time ./tcpsendfile lander 5400 /usr/lib/libc_pic.a -r8 -s -b4096 -sendfile
0.026u 0.172s 0:08.93 2.1% 36+276k 0+0io 0pf+0w
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications & God knows what else.
<dillon@backplane.com> (Please include original email in any response)
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