On 02/22/2017 10:54 AM, Cyrill Gorcunov wrote: > On Wed, Feb 22, 2017 at 10:44:07AM +0300, Pavel Emelyanov wrote: >> On 02/21/2017 10:16 PM, Cyrill Gorcunov wrote: >>> On Tue, Feb 21, 2017 at 10:41:12AM -0800, Andy Lutomirski wrote: >>>>> Thus lets add file position, inode and device number where >>>>> this target lays. This three fields can be used as a primary >>>>> key for sorting, and together with kcmp help CRIU can find >>>>> out an exact file target (from the whole set of processes >>>>> being checkpointed). >>>> >>>> I have no problem with this, but I'm wondering whether kcmp's ordered >>>> comparisons could also be used for this purpose. >>> >>> Yes it can, but it would increas number of kcmp calls signisicantly. >> >> Actually it shouldn't. If you extend the kcmp argument to accept the >> epollfd:epollslot pair, this would be effectively the same as if you >> had all your epoll-ed files injected into your fdtable with "strange" >> fd numbers. We already have two-level rbtree for this in criu, adding >> extended ("strange") fd to it should be OK. > > Nope. Pavel, I guess you forget how we handle file tree in criu currently. > We call for kcmp only if we have to -- when primary key for two entries > is the same. True, but the latter is an optimization to reduce the number of syscalls. Look, in order to have a primary key you need to do some system call for the fd you check (read from proc or stat the descriptor). But for target files in e-polls you don't make this per-fd syscall to get primary key, just call the kcmp instead. -- Pavel -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html