Hello,
since I switched from 2.2.15 to 2.4.0-test-acX (X is currently 12), I
noticed a significant but subjective slow down in interactive
performance. Under Linux2.2, when I hit some key (I telneted to the
box), the reaction (printing the appropriate character) always came
promptly, even if the box was busy (seti@home, kernel compile, etc).
Normally, you did not "feel" that you use telnet due to latency.
But since using 2.4, there are sometimes seconds between hitting the
key and printing the result. Now I ran a md5sum (besides a kernel
compile and seti) and encountered the same problem, and top showed me
this:
6:07pm up 1 day, 23:05, 5 users, load average: 4.84, 3.08, 2.23
77 processes: 73 sleeping, 4 running, 0 zombie, 0 stopped
CPU states: 24.1% user, 13.9% system, 0.3% nice, 63.2% idle
Mem: 38368K av, 37596K used, 772K free, 0K shrd, 984K
buff
Swap: 120956K av, 33524K used, 87432K free 18332K
cached
PID USER PRI NI SIZE RSS SHARE STAT LIB %CPU %MEM TIME
COMMAND
12183 root 19 0 180 136 108 R 0 29.1 0.3 1:28
md5sum
2 root 1 0 0 0 0 DW 0 1.8 0.0 3:26
kswapd
12283 root 2 0 848 848 656 R 0 1.7 2.2 0:00 top
1231 root 1 0 1400 624 476 D 0 1.3 1.6 0:35
named
12308 root 0 0 1168 1156 900 S 0 0.5 3.0 0:00
sendmail
12309 root 0 0 1168 1156 900 S 0 0.4 3.0 0:00
sendmail
735 squid 0 0 8596 676 352 S 0 0.3 1.7 9:56
squid
799 seti 12 12 13796 7312 2036 R N 0 0.3 19.0 2574m
setiathome
I was somewhat... puzzled, because normally linux would use the
available resources appropriately, but because the CPU was 63.2% idle,
this obviously was wrong. I was used to "overload" the memory with
seti and the like, now I have to kill seti in order to have good
kernel compile speed.
I think the virtual memory management is not optimal for the "memory
overload" case. I assume that the kernel swaps out pages too
aggressively, making them unavailable in the next second.
Does anybody has a ready to run swap-benchmark program? I'd like to
run it and prove the difference.
Xuân. :o)
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This archive was generated by hypermail 2b29 : Thu Jun 15 2000 - 21:00:25 EST