From: Linus Torvalds Date: Thu, 23 Jul 2009 03:47:10 GMT Subject: Re: Performance issue of 'git branch' Message-ID: In-Reply-To: <20090723031843.GA9152@Pilar.aei.mpg.de> On Thu, 23 Jul 2009, Carlos R. Mafra wrote: > > PS: Out of curiosity, how many femtoseconds does it take in your > state-of-the-art machine? :-) Cold cache? 0.15s before the patch. 0.03s after. So we're not talking femto-seconds, but I've got Intel SSD's that do random reads in well under a millisecond. Your pitiful 4200rpm drive probably takes 20ms for each seek. You don't really need that many IO's for it to take a second or two. Or four. The kernel will do IO in bigger chunks than a single page, and there is _some_ locality to it all, so you won't see IO for each lookup. But with 2000+ lines of GIT_DEBUG_LOOKUP, you probably do end up having a noticeable fraction of them being IO-causing, and another fraction causing seeks. But I'll see if I can dig up my non-binary-search patch and see if I can make it go faster. My machine is fast, but not so fast that I can't measure it ;) Linus