Messages in this thread |  | | Date | Thu, 30 Jul 2015 22:16:56 -0400 | | From | Waiman Long <> | | Subject | Re: [PATCH] proc: change proc_subdir_lock to a rwlock |
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On 07/29/2015 06:21 PM, Eric W. Biederman wrote: > Two quick questions. > > - What motivates this work? Are you seeing lots of > parallel reads on proc?
The micro-benchmark that I used was artificial, but it was used to reproduce an exit hanging problem that I saw in real application. In fact, only allow one task to do a lookup seems too limiting to me. > - Why not rcu? Additions and removal of proc generic > files is very rare. Conversion to rcu for reads should > perform better and not take much more work.
RCU is harder to verify its correctness, whereas rwlock is easier to use and understand. If it is really a performance critical path where every extra bit of performance counts, I will certainly think RCU may be the right choice. However, in this particular case, I don't think using RCU will give any noticeable performance gain compared with a rwlock.
Cheers, Longman
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