On Thu, Apr 30, 2020 at 04:11:18PM -0400, Daniel Jordan wrote: > Sometimes the kernel doesn't take full advantage of system memory > bandwidth, leading to a single CPU spending excessive time in > initialization paths where the data scales with memory size. > > Multithreading naturally addresses this problem, and this series is the > first step. > > It extends padata, a framework that handles many parallel singlethreaded > jobs, to handle multithreaded jobs as well by adding support for > splitting up the work evenly, specifying a minimum amount of work that's > appropriate for one helper thread to do, load balancing between helpers, > and coordinating them. More documentation in patches 4 and 7. > > The first user is deferred struct page init, a large bottleneck in > kernel boot--actually the largest for us and likely others too. This > path doesn't require concurrency limits, resource control, or priority > adjustments like future users will (vfio, hugetlb fallocate, munmap) > because it happens during boot when the system is otherwise idle and > waiting on page init to finish. > > This has been tested on a variety of x86 systems and speeds up kernel > boot by 6% to 49% by making deferred init 63% to 91% faster. Patch 6 > has detailed numbers. Test results from other systems appreciated. > > This series is based on v5.6 plus these three from mmotm: > > mm-call-touch_nmi_watchdog-on-max-order-boundaries-in-deferred-init.patch > mm-initialize-deferred-pages-with-interrupts-enabled.patch > mm-call-cond_resched-from-deferred_init_memmap.patch > > All of the above can be found in this branch: > > git://oss.oracle.com/git/linux-dmjordan.git padata-mt-definit-v1 > https://oss.oracle.com/git/gitweb.cgi?p=linux-dmjordan.git;a=shortlog;h=refs/heads/padata-mt-definit-v1 For the series (and the three prerequisite patches): Tested-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Thank you for writing this, and thank you for working towards upstreaming it!
