Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH V2 2/2] module: Fix performance regression on modules with large symbol tables | Date | Wed, 16 Nov 2011 10:54:27 +1030 |
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On Mon, 14 Nov 2011 08:48:52 +0000, "Jan Beulich" <JBeulich@suse.com> wrote: > > + name = &mod->strtab[src->st_name]; > > + if (unlikely(!test_bit(src->st_name, info->strmap))) { > > + /* Symbol name has already been copied; find it. */ > > + char *dup; > > + > > + for (dup = mod->core_strtab; strcmp(dup, name); dup++) > > + BUG_ON(dup > s); > > Aren't you concerned that this again will be rather slow? It would be > pretty easy to accelerate by comparing only with the tail of each string > (as nothing else can possibly match), moving from string to string instead > of from character to character.
Kevin's central thesis is that this is actually really unusual.
I'm not sure how much faster a tail search would be in practice. We're still scanning the string. Perhaps a "dup[0] == name[0] &&" would optimize it almost as well, if gcc doesn't already?
Kevin, you're probably in an optimal position to get numbers on this?
Thanks, Rusty.
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