On Thu, 02 Oct 2014 14:07:37 -0700 [email protected] (Eric W. Biederman) wrote:
> Alexey Dobriyan <[email protected]> writes: > > > On Thu, Oct 02, 2014 at 11:01:50AM -0700, Eric W. Biederman wrote: > >> Nicolas Dichtel <[email protected]> writes: > >> > >> > From: Thierry Herbelot <[email protected]> > >> > > >> > The current implementation for the directories in /proc is using a single > >> > linked list. This is slow when handling directories with large numbers of > >> > entries (eg netdevice-related entries when lots of tunnels are opened). > >> > > >> > This patch enables multiple linked lists. A hash based on the entry name > >> > is > >> > used to select the linked list for one given entry. > >> > > >> > The speed creation of netdevices is faster as shorter linked lists must > >> > be > >> > scanned when adding a new netdevice. > >> > >> Is the directory of primary concern /proc/net/dev/snmp6 ? > >> > >> Unless I have configured my networking stack weird by mistake that > >> is the only directory under /proc/net that grows when we add an > >> interface. > >> > >> I just want to make certain I am seeing the same things that you are > >> seeing. > >> > >> I feel silly for overlooking this directory when the rest of the > >> scalability work was done. > > > > Slowdown comes from "duplicate name" check: > > > > for (tmp = dir->subdir; tmp; tmp = tmp->next) > > if (strcmp(tmp->name, dp->name) == 0) { > > WARN(1, "proc_dir_entry '%s/%s' already > > registered\n", > > dir->name, dp->name); > > break; > > } > > > > Removal can be made O(1) after switching to doubly-linked list. > > Yes. There is the however unfortunate fact that proc directories exist > to be used. If we don't switch to a better data structure than a linked > list the actual use will then opening of the files under > /proc/net/dev/snmp6/ will become O(N^2). Which doesn't help much > (assuming those files are good for something). > > If those files aren't actually useful we should just make registering > them a config option. Deprecate them strongly and let only people who > need extreme backwards compatibility enable them. Net-snmp uses them (agent/mibgroup/mibII/kernel_linux.c) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
