Messages in this thread | | | From | Mihai Maruseac <> | Date | Mon, 10 Oct 2011 11:43:20 +0300 | Subject | Re: [PATCH] dev: use name hash for dev_seq_ops. |
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On Fri, Oct 7, 2011 at 7:24 PM, Stephen Hemminger <shemminger@vyatta.com> wrote: > On Fri, 7 Oct 2011 18:20:49 +0300 > Mihai Maruseac <mihai.maruseac@gmail.com> wrote: > >> Instead of using the dev->next chain and trying to resync at each call to >> dev_seq_start, use this hash and store bucket number and bucket offset in >> seq->private field. >> >> As one can notice the improvement is of 1 order of magnitude. > > Good idea, > This will change the ordering of entries in /proc which may upset > some program, not a critical flaw but worth noting. > > Rather than recording the bucket and offset of last entry, another > alternative would be to just record the ifindex. >
I tried to record the ifindex but I think that using it and dev_get_by_index can result in an infinite loop or a NULL dereferrence. If a device is removed and ifindex points to it we'll get a NULL from dev_get_by_index. Checking for NULL and calling again dev_get_by_index will end in an infinite loop at the end of the hlist.
Augmenting the structure to also contain the number of indexes when the seq_file is opened returns to the current situation with two ints. Also, it is more prone to bugs caused by device removal while printing.
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