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From: | Anand Avati |
Subject: | Re: [Gluster-devel] [RFC ] dictionary optimizations |
Date: | Tue, 3 Sep 2013 00:33:08 -0700 |
Hi,
dict_t structures are widely used in glusterfs. I've some ideas that could improve its performance.
* On delete operations, return the current value if it exists.
This is very useful when we want to get a value and remove it from the dictionary. This way it can be done accessing and locking the dict_t only once (and it is atomic).
* On add operations, return the previous value if it existed.
This avoids to use a lookup and a conditional add (and it is atomic).
* Always return the data_pair_t structure instead of data_t or the data itself.
This can be useful to avoid future lookups or other operations on the same element. Macros can be created to simplify writing code to access the actual value.
* Use a trie instead of a hash.
A trie structure is a bit more complex than a hash, but only processes the key once and does not need to compute the hash. A test implementation I made with a trie shows a significant improvement in dictionary operations.
* Implement dict_foreach() as a macro (similar to kernel's list_for_each()).
This gives more control and avoids the need of helper functions.
Additionally, I think it's possible to redefine structures to reduce the number of allocations and pointers used for each element (actual data, data_t, data_pair_t and key).
What do you think ?
Best regards,
Xavi
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