> -----邮件原件----- > 发件人: Honnappa Nagarahalli [mailto:honnappa.nagaraha...@arm.com] > 发送时间: 2020年5月14日 9:22 > 收件人: Lilijun (Jerry) <jerry.lili...@huawei.com>; 'dev@dpdk.org' > <dev@dpdk.org> > 抄送: wangyunjian <wangyunj...@huawei.com>; xudingke > <xudin...@huawei.com>; 'sta...@dpdk.org' <sta...@dpdk.org>; nd > <n...@arm.com>; yipeng1.w...@intel.com; Honnappa Nagarahalli > <honnappa.nagaraha...@arm.com>; nd <n...@arm.com> > 主题: RE: [dpdk-dev] [PATCH] lib/librte_hash: add rte_hash_del_key_fixed > without compact > > <snip> > > > > > > > > > > > Adding Yipeng, maintainer for hash library > > > > > > > > > > > > > > > > > Thanks for your reply. > > > > > > > > > > > > Using rte_hash iterate and delete keys is to free the related > > > > > > data's > > > > memory. > > > > > > There are two reasons why rte_hash_reset() is not properly: > > > > > > 1) the reset function just clear all keys, the key's related > > > > > > data are > > > leaked. > > > > > That is a good point. I think this should be documented in the API. > > > > > > > > > > > 2) In some cases, I don't need delete all keys. Just some > > > > > > selected keys and data are deleted and released. > > > > > I understand the problem you have pointed out and understand how > > > > > to reproduce it. But, the use case is not clear to me. Can you > > > > > please explain the use case? > > > > [Lilijun (Jerry)] > > > > > > > > As you know, the dpdk rte_hash use a fixed size table to store all > > > keys/datas. > > > > The memory used by hash table is related with this fixed size. > > > > In my case, normally the count of keys is about 100,000 but > > > > sometimes the count may burst up to 30,000,000. > > > > In order to save memory usage, I create a small hash table with > > > > 100,000 size and replace to a bigger one with 30,000,000 size when > > > > there are more keys to be stored. Also when the key's count > > > > reduced to less than 100,000, I replace the hash table with a > > > > small one to save the > > > memory. > > > Thank you for explaining this. What happens to the reader when you > > > are deleting from old table and inserting in the new one? Which > > > table does the reader lookup from? > > [Lilijun (Jerry)] > > Lookup functions works well at any time. The problem is in > > rte_hash_iterate() functions. Some example codes like this: > > *next = 0; > > //If rh has 10000 entries at first. > > while ((idx = rte_hash_iterate(rh, key, data, next)) >= 0) { > > rte_hash_del_key(rh, key); //BUT HERE maybe only delete > > 9990 keys !!! > > free(*data); > > } > > //There are still 10 key/datas not freed and will be leaked. > > rte_hash_free(rh); > I understand this problem. > I am trying to understand if there are other problems in the process you are > following. > For ex: when you are transferring an entry from the old table, if the reader > is > looking up from the old table, the entry will not be found, even though the > entry is available in the new table. Can this happen? > [Lilijun (Jerry)] Your example may be happen if read and resize are in two thread context and it's like a RCU cases. But I think it can be fixed for reader can retry the lookup or use a read-lock while resize using a write-lock.
> <snip the diff>
