On Thu, Aug 25, 2016 at 05:56:25PM +0000, Ben Maurer wrote: > rseq opens up a whole world of algorithms to userspace – algorithms > that are O(num CPUs) and where one can have an extremely fast fastpath > at the cost of a slower slow path. Many of these algorithms are in use > in the kernel today – per-cpu allocators, RCU, light-weight reader > writer locks, etc. Even in cases where these APIs can be implemented > today, a rseq implementation is often superior in terms of > predictability and usability (eg per-thread counters consume more > memory and are more expensive to read than per-cpu counters). > > Isn’t the large number of uses of rseq-like algorithms in the kernel a > pretty substantial sign that there would be demand for similar > algorithms by user-space systems programmers? Yes and no. It provides a substantial sign that such algorithms could and should exist; however "someone should do this" doesn't demonstrate that someone *will*. I do think we need a concrete example of a userspace user with benchmark numbers that demonstrate the value of this approach. Mathieu, do you have a version of URCU that can use rseq to work per-CPU rather than per-thread? URCU's data structures would work as a benchmark. Ben, Mathieu, Dave, do you have jemalloc benchmark numbers with and without rseq? (As well as memory usage numbers for the reduced memory usage of per-CPU pools rather than per-thread pools?) -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
