emin ak wrote:
Dear all,
Today I have tried Ingo Molnar's patch-2.6.16-rt10 on a ppc (PQ3 MPC8540ADS)
For testing purpose I have enabled packet routing and send ethernet
packets over the system with a network test equipment. under light
load on ethernet, the system is working fine, but under heavy load,
firstly console freezes, then the message below prints on the console
again and again. The system without patch is working fine on light or
heavy loads. What can be the problem, is there a bug or am i doing
something wrong?
Thanks alot..
here is the console output
--------------------------console output-----
softirq-net-rx/: page allocation failure. order:0, mode:0x20
Call Trace:
[C04E3DB0] [C000A60C] show_stack+0x50/0x188 (unreliable)
[C04E3DE0] [C004C3EC] __alloc_pages+0x1c8/0x2a4
[C04E3E30] [C0063C90] cache_alloc_refill+0x35c/0x57c
[C04E3E80] [C0063FA4] __kmalloc+0xf4/0xfc
[C04E3EB0] [C012D460] __alloc_skb+0x58/0x118
[C04E3ED0] [C011AF20] gfar_new_skb+0x40/0xd4
[C04E3EF0] [C011D320] gfar_clean_rx_ring+0x25c/0x634
[C04E3F30] [C011D72C] gfar_poll+0x34/0x140
[C04E3F50] [C013364C] net_rx_action+0x94/0x188
[C04E3F80] [C0026730] ksoftirqd+0x104/0x1b4
[C04E3FC0] [C003779C] kthread+0xf8/0x100
[C04E3FF0] [C0004DB8] kernel_thread+0x44/0x60
Mem-info:
DMA per-cpu:
cpu 0 hot: high 90, batch 15 used:0
cpu 0 cold: high 30, batch 7 used:0
DMA32 per-cpu: empty
Normal per-cpu: empty
HighMem per-cpu: empty
Free pages: 768kB (0kB HighMem)
Active:1650 inactive:2036 dirty:0 writeback:0 unstable:0 free:192
slab:60106 mapped:764 pagetables:29
DMA free:768kB min:2048kB low:2560kB high:3072kB active:6600kB
inactive:8144kB present:262144kB pages_scanned:0 all_unreclaimab
le? no
lowmem_reserve[]: 0 0 0 0
You have plenty of memory that should be reclaimable (active+inactive,
though
some may be mlocked or otherwise unreclaimable).
What it looks like is that the page reclaim is not able to take place,
because
all your allocations are coming from interrupt context.
Normally what will happen is that kswapd will be woken up, and ksoftirqd
will
start throttling (soft) interrupts and kswapd will be allowed to get a
chance
to run. With the -rt kernel, I guess if your network irq has a higher
priority
than kswapd, it could prevent it from running completely. (I could be wrong
here).
You might try increasing /proc/sys/vm/min_free_kbytes, or failing that,
increase
the priority of kswapd to something comparable to or greater than your
network
interrupt.
I'm not very familiar with the -rt tree, but possibly what should be
happening,
if interrupts are executed in process context and allowed to schedule,
is that
their memory allocations should also be allowed to reclaim memory.
OTOH, I guess for a deterministic realtime system, you need to allocate
fixed
minimum amounts of memory for each element of the system so you never
run out
like this.
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