Messages in this thread | | | Date | Tue, 28 Mar 2017 18:58:54 +0800 | From | zhouchengming <> | Subject | Re: [PATCH] reduce the time of finding symbols for module |
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On 2017/3/28 17:00, Miroslav Benes wrote: > > Hi, > > On Tue, 28 Mar 2017, Zhou Chengming wrote: > >> It's reported that the time of insmoding a klp.ko for one of our >> out-tree modules is too long. >> >> ~ time sudo insmod klp.ko >> real 0m23.799s >> user 0m0.036s >> sys 0m21.256s > > Is this stable through several (>=10) runs? 23 seconds are really > suspicious. Yes, there is a linear search through all the kallsyms in > kallsyms_on_each_symbol(), but there are something like 70k symbols on my > machine (that is, way less than 1M). 23 seconds are somewhat unexpected. >
Yes, it's stable through several runs.
I think the big reason is that our out-tree module used a lot of static local variables. We can see '.rela.kpatch.dynrelas' contains many entries, so it will waste a lot of time if we use kallsyms_on_each_symbol() to find these symbols of module.
Relocation section '.rela.kpatch.funcs' at offset 0x382e0 contains 3 entries: Offset Info Type Sym. Value Sym. Name + Addend 000000000000 003300000101 R_AARCH64_ABS64 0000000000000000 value_show + 0 000000000020 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 8 000000000028 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 0
Relocation section '.rela.kpatch.dynrelas' at offset 0x38328 contains 2562 entries: Offset Info Type Sym. Value Sym. Name + Addend 000000000000 003300000101 R_AARCH64_ABS64 0000000000000000 value_show + 14 000000000018 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 13 000000000020 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 0 000000000040 003300000101 R_AARCH64_ABS64 0000000000000000 value_show + 20 000000000058 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 13 000000000060 000b00000101 R_AARCH64_ABS64 0000000000000000 .kpatch.strings + 0
> If it is a problem, can we fix kallsyms_on_each_symbol() and replace the > linear search with something better? All users would benefit... >
Yes, it's better if we can improve the linear search, but I can't think of that...
Thanks.
> Thanks, > Miroslav > > . >
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