[gentoo-dev] kernel performace/responsiveness issues under heavy loads

[Miguel S. Filipe]

Hi there, I have big performance issues with the gentoo kernels, both
2.4.17-r5 and 2.4.19-r1.
My system is a SMP machine (dual-athlon) with only 256MB of ddr ram.
(so.. I swap a lot, 1gb swap partition)
The system is pretty up to date. and spread around two disks(both with a
similar performance of 15-18MB/s), 1 for the /home and swap partition,
another for the "/". The filesystem is reiserfs, Window Manager: kde3

The problem:
While running heavy aplications:
  kde3, robocode(java), netbeans(java IDE), mozilla, and others like,
konqueror, xmms, xchat, gkrellm.. and konsole.
please note that java is sun's jre-1.4.0 (the faster one around,
acondingly to my benchmarks)

Something like 140 processes.
Some use plenty of ram: 59M(java),31M(mozilla-bin),28M(X), 19M(java)

while, kernel compiling, running championchips in robocode (very
intensive java aplication, with a lots of processes  and ram (robots
fighting each other in a arena)), web browsing with konqueror, checking
email with mozilla-mail
and the other apps are normal apps, xmms is very good to check system
latency because its playing music(so we notice when things start to "hand")

Basically, the system was so unresponsive that I had to close everything
but robocode, wich crashed at the end.

Now, i have my own kernel, 2.4.18 with o(1)-scheduler-k3, preempt-patch,
and nothing else.
I'm reproducing the load and the system is quite fine, obviously this
isn't super-responsive, but its usable.

here's a sample of vmstat:
--(m3thos#:~/robocode/robots)-- vmstat 5
    procs                      memory    swap          io
system         cpu
  r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us
sy  id
  7  1  0 314508  66424  10164  28856  30  25    75    77  150  1416
32   5  63
25  0  0 314508  18304  12384  30044   9   0   194   815  334  7721  70
11  19
  6  0  0 314508  53764  13616  30836   0   0    70   530  298  3074
92   7   1
  3  5  1 314508  61260  14624  32360 1294   0  1495   360  378  3939
86   8   6
  8  1  0 314508  33216  14700  35216 2290   0  2807    69  518  3004
91   7   1
16  4  0 314508  19588  15816  37464 310   0   600   503  336  4516  80
10  10
17  2  0 314516   9172   8696  30876 105  25   198   851  330  2903
91   9   0
11  0  0 314516  10644   9696  31540  86   0   175   434  315  2849
94   6   0
10  1  1 316252  30228   8336  29592 729 374   874   766  357  3552
93   7   0
  8  0  1 316252  30968   8404  30432 526   0   640   141  339  6229
92   8   0
  8  0  0 316252  52048   9320  31956 1966   0  2053   415  398  6080
83   8   8

here's a sample of free:
--(m3thos#:~/robocode/robots)-- free
              total       used       free     shared    buffers     cached
Mem:        255660     237400      18260          0       6680      24328
-/+ buffers/cache:     206392      49268
Swap:      1225996     318812     907184
heres the uptime:
--(tigre)-(pts1)-(22:04/09-Apr-02)--
--(m3thos#:~/robocode/robots)-- uptime
  10:08pm  up  4:04,  1 user,  load average: 17.72, 15.03, 10.99


and I'm attaching the config file that it's being used

I'v noticed first in 2.4.17-r5 that responsive was flacky, and after
upgrading to 2.4.19 saw that it was still pretty bad under high loads,
but after my own kernel the responsiveness increased a lot!

I'm sending this mail to this ML because I think that this conserns the
kernel mantainers, and all developers since a bat base kernel in terms
of responsiveness is not a good thing to such a "performance oriented"
distribution.
p.s.: obviously that I don't normally have this kind of high loads, but
.. some times I do, and not only for testing(has this time), but also on
current use(has was the time I experimented big responsiveness issues
with 2.4.19-r1).


Thank you all!
Great Distro!

Miguel Sousa Filipe
handle: m3thos
More human than human
(PORTUGAL)