On Wed, Aug 24, 2016 at 2:30 PM, Tejun Heo <t...@kernel.org> wrote: > Hello, John. > > On Wed, Aug 24, 2016 at 02:16:52PM -0700, John Stultz wrote: >> Hey Peter, Tejun, Oleg, >> So while you're tweaks for the percpu-rwsem have greatly helped the >> regression folks were seeing (many thanks, by the way), as noted >> above, the performance regression with the global lock compared to >> earlier kernels is still ~3x slower (though again, much better then >> the 80x slower that was seen earlier). >> >> So I was wondering if patches to go back to the per signal_struct >> locking would still be considered? Or is the global lock approach the >> only way forward? > > We can't simply revert but we can make the lock per signal_struct > again. It's just that it'd be quite a bit more complex (but, again, > if we need it...) and for cases where migrations aren't as frequent > percpu-rwsem would be at least a bit lower overhead. Can you please > test with the following patch applied just in case? > > > https://git.kernel.org/cgit/linux/kernel/git/tj/cgroup.git/commit/?h=for-4.8-fixes&id=568ac888215c7fb2fabe8ea739b00ec3c1f5d440
Hey! Good news. This patch along with Peter's locking changes pushes the latencies down to an apparently acceptable level! Many thanks for the pointer! thanks -john