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SubjectRe: Strange load issues with 2.5.69/70 in both -mm and -bk trees.
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On Mon, 2003-06-02 at 03:36, Ingo Molnar wrote:
> On Sat, 31 May 2003, Andrew Morton wrote:
>
> > > [...] Upon looking a little further it
> > > seemed that the kernel was dynamically boosting the priority of the
> > > process much higher than it probably should be, in the end, not leaving
> > > enough CPU for playing the sounds without skipping.
> >
> > Yes, it seems that too many real-world applications are accidentally
> > triggering this problem.

Not sure if what I'm seeing is the same thing, Without using wine, weird
mozilla plugins, or a userspace mixer/sound server (audigy with hardware
mixing).

During the first few seconds of playing a song in xmms sound will skip
if even just loading or refreshing a page in mozilla, though after the
song has been playing a few seconds it will stop skipping for the
duration of that song, until the next song in the playlist starts
playing. renicing -5 <pid of xmms>, or 5 <pid of mozilla> 'solves' the
issue. Ofcourse, if mozilla is the reniced process, xmms may still skip
when switching desktops, again that is much more likely to occur during
the first few seconds of playtime than later in the song. I cant recall
xmms ever skipping after it has been reniced to -5, even if I also have
a real cpu hog running (oggenc or similar).

Also, if nothing has been reniced and I swith desktops around like mad
for a while xmms will stop skipping even when switching to the next song
in the playlist, i suppose X/the wm/mozilla/etc has all been scheduled
off as cpu hogs by the exessive desktop switching..

I cant remember when this became really noticable, but it was probably
in the 2.5.68 timeframe. I am running 2.5.69-mm8+schedB0 at the moment
(software raid1 keeps me from going to 2.5.70-*)

a strace of mozilla shows that even when it is just sitting there
without a page loaded this stuff is just looping:

15:37:35.808520 ioctl(3, FIONREAD, [0]) = 0
15:37:35.808584 poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN,
revents=POLLIN}], 2, -1) = 1
15:37:36.308127 gettimeofday({1054582656, 308165}, NULL) = 0
15:37:36.308311 read(4, "\372", 1) = 1
15:37:36.308396 write(3,
"F\4\5\0l\0\240\1\332\0\240\1\355\0)\0\1\0\20\0", 20) = 20
The below `vmstat 1` was started just before xmms -p. I then switched
desktops for a while until xmms stopped skipping.:

procs memory swap io
system cpu
r b w swpd free buff cache si so bi bo in cs us
sy id
2 0 0 10416 47560 18728 230860 2 1 68 1 66 58 6
2 11
0 0 0 10416 47424 18728 230860 0 0 0 0 1371 1185 12
11 77
0 0 0 10416 47424 18728 230860 0 0 0 33 1372 906 5
6 89
1 0 0 10416 47352 18728 230860 0 0 0 0 1413 1984 21
9 70
1 0 0 10416 47464 18728 230860 0 0 0 0 1927 1925 55
12 33
2 0 0 10416 47168 18728 230860 0 0 0 0 1185 1011 74
11 15
3 0 0 10416 44416 18728 230860 0 0 0 0 1182 1516 33
6 61
1 0 0 10416 47348 18728 230860 0 0 0 0 1171 1041 80
16 4
3 0 0 10416 45044 18728 230860 0 0 0 0 1195 1327 44
13 44
3 0 0 10416 47348 18728 230860 0 0 0 0 1173 1049 54
10 36
2 0 0 10416 46712 18728 230860 0 0 0 0 1186 1206 65
11 24
2 0 0 10416 30264 18728 230860 0 0 0 0 1190 1152 46
10 44
1 0 0 10416 47212 18728 230860 0 0 0 0 1168 1058 75
10 15
2 0 0 10416 47212 18728 230860 0 0 0 0 1184 1463 3
5 92
3 0 0 10416 36900 18728 231020 0 0 0 0 1183 1114 65
11 24
1 0 0 10416 47268 18728 230860 0 0 0 0 1176 1370 23
5 72
2 0 0 10416 24360 18728 230860 0 0 0 0 1192 1467 30
7 63
1 0 0 10416 47220 18728 230860 0 0 0 0 1189 1163 63
11 26
1 0 0 10416 47220 18728 230860 0 0 0 0 1184 1624 2
5 93
4 0 0 10416 43828 18728 230860 0 0 0 0 1193 1202 31
5 64
1 0 0 10416 47224 18728 230860 0 0 0 0 1173 1190 57
11 32
procs memory swap io
system cpu
r b w swpd free buff cache si so bi bo in cs us
sy id
3 0 0 10416 47224 18728 230860 0 0 0 0 1184 1513 1
1 98
3 0 0 10416 17620 18728 244360 0 0 0 0 1195 893 66
11 23
3 0 0 10416 37304 18728 230860 0 0 0 0 1194 1277 45
10 45
2 0 0 10416 47224 18728 230860 0 0 0 0 1189 1147 84
16 0
2 0 0 10416 42552 18728 230860 0 0 0 0 1194 1867 84
15 1
2 0 0 10416 47224 18728 230860 0 0 0 0 1485 2230 20
5 75
1 0 0 10416 47232 18728 230860 0 0 0 0 1325 1629 1
2 97
0 0 0 10416 47232 18728 230860 0 0 0 0 1373 1168 13
8 79
1 0 0 10416 47232 18728 230860 0 0 0 0 1163 551 1
2 97


> no, the problem is exactly the opposite. Here's the key observation:
>
> > the problem seemed to be caused by the fact that the pluginserver (wine)
> > was using 100% of the CPU. I simply reniced this process to -10 and
> > everything started working fine.
>
> the kernel has detected this process to be a CPU-hog - and indeed the
> traces and the above description all say that it really is a CPU hog.

What I am seeing happens if the box has a load avg of 0.1 or 2.0, in a
pretty much identical fasion.

Andreas

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