On 12/07/2018 04:03 PM, David Miller wrote:
> From: David Ahern <dsah...@kernel.org>
> Date: Fri, 7 Dec 2018 12:24:57 -0800
>
>> From: David Ahern <dsah...@gmail.com>
>>
>> The existing garbage collection algorithm has a number of problems:
> ...
>> This patch addresses these problems as follows:
>>
>> 1. Use of a separate list_head to track entries that can be garbage
>> collected along with a separate counter. PERMANENT entries are not
>> added to this list.
>>
>> The gc_thresh parameters are only compared to the new counter, not the
>> total entries in the table. The forced_gc function is updated to only
>> walk this new gc_list looking for entries to evict.
>>
>> 2. Entries are added to the list head at the tail and removed from the
>> front.
>>
>> 3. Entries are only evicted if they were last updated more than 5 seconds
>> ago, adhering to the original intent of gc_thresh2.
>>
>> 4. Forced gc is stopped once the number of gc_entries drops below
>> gc_thresh2.
>>
>> 5. Since gc checks do not apply to PERMANENT entries, gc levels are skipped
>> when allocating a new neighbor for a PERMANENT entry. By extension this
>> means there are no explicit limits on the number of PERMANENT entries
>> that can be created, but this is no different than FIB entries or FDB
>> entries.
>>
>> Signed-off-by: David Ahern <dsah...@gmail.com>
>> ---
>> v2
>> - remove on_gc_list boolean in favor of !list_empty
>> - fix neigh_alloc to add new entry to tail of list_head
>
> Again, looks great, applied.
>
What protects gc_list linkage ?
We can not use list_del_init(&n->gc_list); or
list_add_tail(&n->gc_list, &n->tbl->gc_list);
if tbl->lock is not held.
It seems to me this patch needs more care.
