On 08/19/16 02:24 PM, Josh Triplett wrote: > On Fri, Aug 19, 2016 at 01:56:11PM -0700, Andi Kleen wrote: > > > Nobody gets a cpu number just to get a cpu number - it's not a useful > > > thing to benchmark. What does getcpu() so much that we care? > > > > malloc is the primary target I believe. Saves lots of memory to keep > > caches per CPU rather than per thread. > > Also improves locality; that does seem like a good idea. Has anyone > written and tested the corresponding changes to a malloc implementation? > I had modified jemalloc to use rseq instead of per-thread caches, and did some testing on one of our services. Memory usage decreased by ~20% due to fewer caches. Our services generally have lots and lots of idle threads (~400), and we already go through a few hoops to try and flush idle thread caches. Threads are often coming from dependent libraries written by disparate teams, making them harder to reduce to a smaller number. We also have quite a few data structures that are sharded thread-locally only to avoid contention, for example we have extensive statistics code that would also be a prime candidate for rseq . We often have to prune some stats because they're taking up too much memory, rseq would let us fit a bit more in. jemalloc diff here (pretty stale now): https://github.com/djwatson/jemalloc/commit/51f6e6f61b88eee8de981f0f2d52bc48f85e0d01 Original numbers posted here: https://lkml.org/lkml/2015/10/22/588 -- 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
