From: Joe Perches
Sent: 07 October 2021 17:28
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IMO: this new file is missing 2 #include directives.
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This is not a self-contained header as it requires #include <linux/build_bug.h> which should be at the top of this file.
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And this requires
#include <linux/err.h>
And I bet the biggest problem is the time spent by the compiler searching down the -I path for headers.
If you count system calls during a build I suspect that failed opens of .h files dominate.
To see how much this really costs try running a build with a (traditional) NFS mounted source tree - where every directory name in a filename requires an NFS file handle lookup.
David
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