On 05/18/2011 12:54 AM, Christoph Hellwig wrote: > On Tue, May 17, 2011 at 04:33:07PM -0700, Tim Bird wrote: >> That said, I can answer Greg's question. This is to speed up >> the symbol resolution on module loading. The last numbers I >> saw showed a reduction of about 15-20% for the module load >> time, for large-ish modules. Of course this is highly dependent >> on the size of the modules, what they do at load time, and how many >> symbols are looked up to link them into the kernel. > > How large are these very large modules, and what are good examples for > that? usbcore seems to be a large-ish module whose load time is improved by this. More details follow: I don't know the exact modules, but Alan Jenkins reported a .3 second reduction in overall boot time, on a EEE PC, presumably running a stock Linux distribution, and loading 41 modules. See http://lkml.org/lkml/2009/11/3/93 Carmelo Amoroso reported some good performance gains in this presentation: http://elinux.org/images/1/18/C_AMOROSO_Fast_lkm_loader_ELC-E_2009.pdf (See slide 22). He doesn't report the overall time savings, and he was using a different method (hash tables as opposed to binary search), but I believe the results are comparable to what the binary search enhancement provides. The biggest offenders in his testing were usbcore, ehci_hcd and ohci_hcd. > And why do people overly care for the load time? To reduce overall boot time. -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
