On Sun, 17 Mar 2024 11:40:54 -0400 "Drew Gallatin" <galla...@freebsd.org> wrote:
> Resending with the patch as an attachment. > > Drew > > On Sun, Mar 17, 2024, at 11:39 AM, Drew Gallatin 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? > > > > 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. > > > > 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. > > > > Drew Controlled via RW or RWTUN sysctl/tunable? -- Tomoaki AOKI <junch...@dec.sakura.ne.jp>
