RE: [for-next][PATCH 12/17] fgraph: Make overruns 4 bytes in graph stack structure

[David Laight]

From: Steven Rostedt
> Sent: 12 November 2020 00:33
> 
> Inspecting the data structures of the function graph tracer, I found that
> the overrun value is unsigned long, which is 8 bytes on a 64 bit machine,
> and not only that, the depth is an int (4 bytes). The overrun can be simply
> an unsigned int (4 bytes) and pack the ftrace_graph_ret structure better.
> 
> The depth is moved up next to the func, as it is used more often with func,
> and improves cache locality.
...
>  } __packed;

Does this many any/much difference given that the structure is
marked __packed?

OTOH the __packed will (probably) kill performance on systems
that don't support mis-aligned accesses.

	David

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