On Wed, Sep 8, 2021 at 5:02 PM Prakash Sangappa <prakash.sangappa@xxxxxxxxxx> wrote: > > Resending RFC. This patchset is not final. I am looking for feedback on > this proposal to share thread specific data for us in latency sensitive > codepath. > > (patchset based on v5.14-rc7) > > Cover letter previously sent: > ---------------------------- > > Some applications, like a Databases require reading thread specific stats > frequently from the kernel in latency sensitive codepath. The overhead of > reading stats from kernel using system call affects performance. > One use case is reading thread's scheduler stats from /proc schedstat file > (/proc/pid/schedstat) to collect time spent by a thread executing on the > cpu(sum_exec_runtime), time blocked waiting on runq(run_delay). These > scheduler stats, read several times per transaction in latency-sensitive > codepath, are used to measure time taken by DB operations. > > This patch proposes to introduce a mechanism for kernel to share thread > stats thru a per thread shared structure shared between userspace and > kernel. The per thread shared structure is allocated on a page shared > mapped between user space and kernel, which will provide a way for fast > communication between user and kernel. Kernel publishes stats in this > shared structure. Application thread can read from it in user space > without requiring system calls. Can these use cases be addressed by creating a perf event (perf_event_open) and mmapping it?
