Re: [dpdk-dev] [PATCH 0/3] New Thread Safe Hash Library

[Neil Horman <nhorman@tuxdriver.com>]

On Thu, Sep 18, 2014 at 11:34:28AM +0100, Pablo de Lara wrote:
> This is an alternative hash implementation to the existing hash library. 
> This patch set provides a thread safe hash implementation, it allows users 
> to use multiple readers/writers working on a same hash table.
> Main differences between the previous and the new implementation are:
> 
> - Multiple readers/writers can work on the same hash table, 
>   whereas in the previous implementation writers could not work 
>   on the table at the same time readers do.
> - Previous implementation returned an index to a table after a lookup. 
>   This implementation returns 8-byte integers or pointers to external data.
> - Maximum entries to be looked up in bursts is 64, instead of 16.
> - Maximum key length has being increased to 128, instead of a maximum of 64.
> 
> Basic implementation:
> 
> - A sparse table containing buckets (64-byte long) with hashes,
>   most of which are empty, and indexes to the second table.
> - A compact table containing keys for final matching, 
>   plus data associated to them.
> 
Thread safe hash tables seem to me like a configuration option rather than a new
library.  Instead of creating a whole new library (with a new API and ABI to
maintain, why not just add thread safety as a configurable option to the
existing hash library.  That saves code space in the DPDK, and reduces
application complexity (as the same api is useable for thread safe and unsafe
hash tables)

Neil