From: Andrew Morton <[EMAIL PROTECTED]> Date: Tue, 7 Nov 2006 11:34:00 -0800
> What Evgeniy means here is that copy_to_user() is slower than memcpy() (on > his machine, with his kernel config, at least). > > Which is kinda weird and unexpected and is something which we should > investigate independently from this project. (Rather than simply going > and bypassing it!) It's straightforward to me. :-) If the kerne memcpy()'s, it uses those nice 4MB PTE mappings to the kernel pages. With copy_to_user() you run through tiny 4K or 8K PTE mappings which thrash the TLB. The TLB is therefore able to hold more of the accessed state at a time if you touch the pages on the kernel side. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
