On Friday 18 November 2011 14:37:43 David Daney wrote: > I noticed when booting MIPS64 kernels that sorting of the main > __ex_table was taking a long time (2,692,220 cycles or 3.3 mS at > 800MHz to be exact). That is not too bad for real silicon > implementations, but when running on a slow simulator, it can be > significant.
i've seen this perf hit in my simulation runs too > Here is more or less what I did: > > o A flag word is added to the kernel to indicate that the __ex_table > is already sorted. sort_main_extable() checks this and if it is > clear, returns without doing the sort. > > o I shamelessly stole code from recordmcount and created a new build > time helper program 'sortextable'. This is run on the final vmlinux > image, it sorts the table, and then clears the flag word. > > Potential areas for improvement: > > o Sort module exception tables too. > > o Get rit of the flag word, and assume that if an architecture supports > build time sorting, that it must have been done. > > o Add support for architectures other than MIPS and x86 i don't see much here that is arch-specific. why have a knob at all ? let's just jump in with both feet and do this for everyone :). -mike
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