To: Chris Mason <chris.mason@...>, Christoph Hellwig <hch@...>
Cc: Arjan van de Ven <arjan@...>, T David Chinner <dgc@...>, Benjamin Herrenschmidt <benh@...>, Ingo Molnar <mingo@...>, Andrew Morton <akpm@...>, Linux Kernel Mailing List <linux-kernel@...>, <Th@...>
Hi,
(Rookie warning goes here.) To me, growing the stack at more or less
random places in the kernel seems to be quite a complicated thing to do
and it will be quite a maintainance burden to find the right spots to
insert stack usage checks. So I'ld say: lose the dynamic aspect.
How about unconditionally switching stacks at some defined points within
the core code of the kernel, just before calling into any driver code,
for example? The 4k-option has separate irq stacks already, why not have
driver stacks too?
I think the most important consideration to keep the stack size small
was that non-order-0 allocations are unreliable under/after memory
pressure due to fragmentation and that this allocation has to be done
for each thread. It is therefore preferable not to do any higher-order
allocations at all, unless there is a fall-back mechanism if the
allocation fails. For higher-order stacks there isn't such a fallback...
Can the system get by (without deadlocks at least in practice) with a
limited number of preallocated but 'large' stacks (in addition to a
small per-thread stack)?
It was discussed that stack space is needed for any sleeping process.
Could it be arranged that this waiting happens on the smallish stack, at
least for the most common cases, while non-waiting activity can use the
big stacks?
Greetings,
Alexander
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Alexander van Heukelum
heukelum@fastmail.fm
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