> On 17. Mar 2024, at 16:39, Drew Gallatin <galla...@freebsd.org> wrote: > > I don't have the full context, but it seems like the complaint is a > performance regression in bonnie++ and perhaps other things when tcp_hpts is > loaded, even when it is not used. Is that correct? Correct. > > If so, I suspect its because we drive the tcp_hpts_softclock() routine from > userret(), in order to avoid tons of timer interrupts and context switches. > To test this theory, you could apply a patch like: > > diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c > index e9a16cd0b36e..54b540c97123 100644 > --- a/sys/kern/subr_trap.c > +++ b/sys/kern/subr_trap.c > @@ -138,7 +138,7 @@ userret(struct thread *td, struct trapframe *frame) > * Software Timer Support for Network Processing" > * by Mohit Aron and Peter Druschel. > */ > - tcp_hpts_softclock(); > + /*tcp_hpts_softclock();*/ > /* > * Let the scheduler adjust our priority etc. > */ > > > If that fixes it, I suspect we should either make this hook optional for > casual users of tcp_hpts(), or add some kind of "last called" timestamp to > prevent it being called over and over and over on workloads which are syscall > heavy. Nuno, can you test that? > > Note that for non-casual users of hpts (like Netflix, with hundreds of > thousands of TCP connections managed by hpts), this call is a huge win, so I > think we'd prefer that it remain in some form. Sure.
Best regards Michael > > Drew
