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On Mon, 09 Jan 2023 17:13:25 +0000,
Shanker Donthineni <sdonthineni@xxxxxxxxxx> wrote:
I'm happy to help with it, but I'm certainly not willing to accept any
sort of new compile-time limit.
Thanks for helping with a scalable solution instead of static
allocation. Please include me whenever patches posted to LKML. I'm
happy to verify on NVIDIA server platforms and provide test
feedback.
I offered to help you. I didn't offer to do the work for you! ;-)
I've looked at the IDR/IDA API. There is no suitable function for
allocating contiguous IDs to replace bitmap API.
__irq_alloc_descs():
mutex_lock(&sparse_irq_lock);
start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS,
from, cnt, 0);
ret = -EEXIST;
Is there any existing API that I can use for allocating contiguous IDs?
I think you should address the problem the other way around, as there
are lower hanging fruits:
- turn the irq_desc_tree radix tree into a XArray
- use the XArray mark feature to reimplement the irqs_resend bitmap
Once you have done that, you have already halved the memory usage.
To implement the allocated_irqs bitmap functionality, you have a
bunch of options:
- make the XArray an allocating XArray, and iterate over XA_FREE_MARK
to find the free range (see how the infiniband subsystem is doing
exactly that)
- use another Xarray mark to annotate the allocated IRQs, find the
distance between two allocations, and use this range if the request
fits (a poor man's variation of the above)
- use a sideband data structure such as the GICv3 LPI allocator, which
is already dealing with range allocation (I'd rather avoid that)
- something else?