Hello All,
Got a mystery here... transferring data over the loopback interface on a old RHAS 2.1 kernel (2.4.9-e.25enterprise) even a modern 2.6.1 kernel, is _very_ slow. When the SO_RCVBUF is set low.
As you can see from the tcpdump below after the session gets going, only one data packet is exchanged every .2 seconds, the sending side of the pipe seems to be waiting for something...
- Anyone have a place to look in the RFCs or such that would explain why it's waiting, for what?
Seems pretty quick to me:
Run while stracing the server:
dd if=/dev/zero bs=1024 | time nc -q 0 localhost 2222
Command exited with non-zero status 1 0.07user 0.88system 0:38.67elapsed 2%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (144major+26minor)pagefaults 0swaps 363244+0 records in 363243+0 records out
Fixed the sample program to setsockopt() the accepted file and straced the server:
dd if=/dev/zero bs=1024 | time nc -q 0 localhost 2222
Command exited with non-zero status 1 0.06user 0.79system 0:30.18elapsed 2%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (144major+26minor)pagefaults 0swaps 277564+0 records in 277563+0 records out
Run while tcpdumping the loopback interface:
dd if=/dev/zero bs=1024 | time nc -q 0 localhost 2222
Command exited with non-zero status 1 0.17user 1.98system 0:21.79elapsed 9%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (145major+27minor)pagefaults 0swaps 818739+0 records in 818738+0 records out
Just let it run a while:
dd if=/dev/zero bs=1024 | time nc -q 0 localhost 2222Command exited with non-zero status 1
0.33user 4.90system 0:23.38elapsed 22%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (144major+26minor)pagefaults 0swaps
2045878+0 records in
2045877+0 records out
-- Ken Herron _______________________________________________ vox-tech mailing list [EMAIL PROTECTED] http://lists.lugod.org/mailman/listinfo/vox-tech
