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    SubjectRe: [PATCH] kprobe: increase kprobe_hash_table size
    Andrew Morton wrote:
    >> I agree that there may be many opinions about what is the best suited size.
    >> Why I chose 512 was that I thought the table (byte) size was less than or
    >> equal 4096 even on 64-bit arch.
    > Well...
    > text data bss dec hex filename
    > 7036 744 9380 17160 4308 kernel/kprobes.o
    > 7048 744 73892 81684 13f14 kernel/kprobes.o
    > That's 64 kbytes more memory. It will be kretprobe_table_locks[] which
    > is hurting here, due to the ____cacheline_aligned.

    Oops! It's really bad.

    > I expected CONFIG_X86_VSMP=y to make this far worse, but fortunately
    > that only affects ____cacheline_internodealigned_in_smp.
    > btw, that array wastes a ton of memory on uniprocessor builds. Using
    > ____cacheline_aligned_in_smp should fix that.
    > Please always check these thigns with /usr/bin/size.

    I see. I'll check that and try to find the best way...

    > btw2, could/should kprobe_table[] and kretprobe_inst_table[] be
    > aggregated into kretprobe_table_locks[]? That would save some memory
    > and might save some cache misses as well?

    Indeed, thank you for good idea.

    > Anyway, enough pos-facto code review. Is this change which you're
    > proposing worth increasing kernel memory usage by 64k?

    Not really. Hmm, I have to investigate more on this problem.

    Thanks a lot.

    Masami Hiramatsu

    Software Engineer
    Hitachi Computer Products (America) Inc.
    Software Solutions Division


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