On 30.05.25 11:34, Jiri Bohac wrote:
On Fri, May 30, 2025 at 11:11:40AM +0200, David Hildenbrand wrote:
On 30.05.25 11:07, Michal Hocko wrote:
On Fri 30-05-25 10:39:39, David Hildenbrand wrote:
On 30.05.25 10:28, Michal Hocko wrote:
[...]
All that being said I would go with an additional parameter to the
kdump cma setup - e.g. cma_sane_dma that would skip waiting and use 10s
otherwise. That would make the optimized behavior opt in, we do not need
to support all sorts of timeouts and also learn if this is not
sufficient.
Makes sense?
Just so I understand correctly, you mean extending the "crashkernel=" option
with a boolean parameter? If set, e.g., wait 1s, otherwise magic number 10?
crashkernel=1G,cma,cma_sane_dma # no wait on transition
But is no wait ok? I mean, any O_DIRECT with any device would at least take
a bit, no?
Of course, there is a short time between the crash and actually triggerying
kdump.
crashkernel=1G,cma # wait on transition with e.g. 10s timeout
In general, would work for me.
I don't like extending the crashkernel= syntax like this.
It would make hooking into the generic parsing code in
parse_crashkernel() really ugly. The syntax is already
convoluted as is and hard enough to explain in the documentation.
Would another boolean flag (on top of the other one you are adding)
really make this significantly more ugly?
Also I don't see how adding a boolean knob is better than adding
one that allows setting any arbitrary timeout. It has less
flexibility and all the drawbacks of having an extra knob.
I guess Michals point is that specifying the higher-level problem and
giving less flexibility mioght actually be less confusing for users.
I am inclined to just setting the fixed delay to 10s for now and
adding a sysfs knob later if someone asks for it.
Would that work for you?
Sure. We could always add such a flag later if it's really a problem for
someone.
--
Cheers,
David / dhildenb
