Re: 2.6.6-rc3-mm2 (4KSTACK)

Arjan van de Ven
2004-05-05T19:51:42Z

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> Is it less pain than making something like a memory allocation which comes
> out of a deep stack? Say, nfs server -> filesystem -> lvm/raid -> fiber channel,
> which itself does something like a writepage into an nfs filesystem and ends
> up in the networking stack? OK, getting back into the filesystem on a
> memory allocation from the block layer should not happen, but you could
> certainly be down in

it's not really much different than the 2.4 kernel already has.
In 2.4 you have a 8Kb stack of which

First 1600 bytes (+/-) are for the task struct
about 4Kb of user context stack
>= 2Kb stack which is needed for irq context (both soft and hard)

In 2.6 with this patch you have

32 bytes for thread info
4Kb minus 32 bytes for context stack
SEPARATE softirq stack of 4K
SEPARATE hardirq stack of 4K

so in a way you have MORE stack space than in 2.4.

Now I'll fully admit the 2Kb is somewhat of a stochast, you only hit it
if you have iptable rules and 2 nic irq's arriving on the same cpu at an
unfortionate moment, but that doesn't mean it's a safe situation.

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