On Mon, 2014-07-14 at 18:14 +0200, Peter Zijlstra wrote: > On Mon, Jul 14, 2014 at 09:10:14AM -0700, Tim Chen wrote: > > On Mon, 2014-07-14 at 12:16 +0200, Peter Zijlstra wrote: > > > On Fri, Jul 11, 2014 at 01:33:04PM -0700, Tim Chen wrote: > > > > This function will help a thread decide if it wants to to do work > > > > that can be delayed, to accumulate more tasks for more efficient > > > > batch processing later. > > > > > > > > However, if no other tasks are running on the cpu, it can take > > > > advantgae of the available cpu cycles to complete the tasks > > > > for immediate processing to minimize delay, otherwise it will yield. > > > > > > Ugh.. and ignore topology and everything else. > > > > > > Yet another scheduler on top of the scheduler. > > > > > > We have the padata muck, also only ever used by crypto. > > > We have the workqueue nonsense, used all over the place > > > And we have btrfs doing their own padata like muck. > > > And I'm sure there's at least one more out there, just because. > > > > > > Why do we want yet another thing? > > > > > > I'm inclined to go NAK and get people to reduce the amount of async > > > queueing and processing crap. > > > > The mult-buffer class of crypto algorithms is by nature > > asynchronous. The algorithm gathers several crypto jobs, and > > put the buffer from each job in a data lane of the SIMD register. > > This allows for parallel processing and increases throughput. > > The gathering of the crypto jobs is an async process and > > queuing is necessary for this class of algorithm. > > How is that related to me saying we've got too much of this crap > already? I was trying to explain why the algorithm is implemented this way because of its batching nature. There is a whole class of async algorithm that can provide substantial speedup by doing batch processing and uses workqueue. The multi-buffer sha1 version has 2.2x speedup over existing AVX2 version, and can have even more speedup when AVX3 comes round. Workqueue is a natural way to implement this. I don't think a throughput speedup of 2.2x is "crap". We are not inventing anything new, but ask for a very simple helper function to know if there's something else running on our cpu to help us make a better decision of whether we should flush the batched jobs immediately. And also asynchronous crypto interface is already used substantially in crypto and has a well established infrastructure. Thanks. Tim -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
