Hi, On 2017/12/07 14:21, Taylor R Campbell wrote: > I dropped this thread on the floor a while ago and I forget what the > status was. I've had a patch sitting in my tree for a while which I > brushed off to put the list update logic in separate functions, as I > think chuq requested a while ago, but still keep it all isolated to > subr_psref.c and avoid defining any new macros. > > If you've measured that SLIST works better -- which would make sense > because the typical bracketed psref_acquire/release nesting makes a > nice LIFO stack of the things so that SLIST_REMOVE should usually be > done in the first iteration -- then I'm happy to replace it by SLIST. > We should just make sure to fix this bug before netbsd-8 goes out! > > Thoughts?
I measure IPv4 forwarding performance your patch(PSREF_LIST) version and SLIST version. At first, the result is quite affected by optimization option "-falign-functions"... Based on this, it seems there is almost no difference between PSREF_LIST and SLIST. However, it seems your patch has large diff... From the point of code stability, smaller diff SLIST version would be better for netbsd-8 branch to fix the bug. Because your patch causes some new ATF failures such as ldp_regen and route_change_ifp (reported by ozaki-r@n.o). We can probably fix them at once but guaranteeing its stability would take more time. The SLIST version patch is following. ==================== diff --git a/sys/kern/subr_psref.c b/sys/kern/subr_psref.c index c3f76ab0e74..9eac19def3f 100644 --- a/sys/kern/subr_psref.c +++ b/sys/kern/subr_psref.c @@ -78,7 +78,7 @@ __KERNEL_RCSID(0, "$NetBSD: subr_psref.c,v 1.7 2017/06/01 02:45:13 chs Exp $"); #include <sys/queue.h> #include <sys/xcall.h> -LIST_HEAD(psref_head, psref); +SLIST_HEAD(psref_head, psref); static bool _psref_held(const struct psref_target *, struct psref_class *, bool); @@ -135,7 +135,7 @@ psref_cpu_drained_p(void *p, void *cookie, struct cpu_info *ci __unused) const struct psref_cpu *pcpu = p; bool *retp = cookie; - if (!LIST_EMPTY(&pcpu->pcpu_head)) + if (!SLIST_EMPTY(&pcpu->pcpu_head)) *retp = false; } @@ -194,7 +194,7 @@ psref_check_duplication(struct psref_cpu *pcpu, struct psref *psref, bool found = false; struct psref *_psref; - LIST_FOREACH(_psref, &pcpu->pcpu_head, psref_entry) { + SLIST_FOREACH(_psref, &pcpu->pcpu_head, psref_entry) { if (_psref == psref && _psref->psref_target == target) { found = true; @@ -250,7 +250,7 @@ psref_acquire(struct psref *psref, const struct psref_target *target, #endif /* Record our reference. */ - LIST_INSERT_HEAD(&pcpu->pcpu_head, psref, psref_entry); + SLIST_INSERT_HEAD(&pcpu->pcpu_head, psref, psref_entry); psref->psref_target = target; psref->psref_lwp = curlwp; psref->psref_cpu = curcpu(); @@ -273,6 +273,7 @@ void psref_release(struct psref *psref, const struct psref_target *target, struct psref_class *class) { + struct psref_cpu *pcpu; int s; KASSERTMSG((kpreempt_disabled() || cpu_softintr_p() || @@ -302,7 +303,9 @@ psref_release(struct psref *psref, const struct psref_target *target, * (as does blocking interrupts). */ s = splraiseipl(class->prc_iplcookie); - LIST_REMOVE(psref, psref_entry); + pcpu = percpu_getref(class->prc_percpu); + SLIST_REMOVE(&pcpu->pcpu_head, psref, psref, psref_entry); + percpu_putref(class->prc_percpu); splx(s); /* If someone is waiting for users to drain, notify 'em. */ @@ -353,7 +356,7 @@ psref_copy(struct psref *pto, const struct psref *pfrom, pcpu = percpu_getref(class->prc_percpu); /* Record the new reference. */ - LIST_INSERT_HEAD(&pcpu->pcpu_head, pto, psref_entry); + SLIST_INSERT_HEAD(&pcpu->pcpu_head, pto, psref_entry); pto->psref_target = pfrom->psref_target; pto->psref_lwp = curlwp; pto->psref_cpu = curcpu(); @@ -474,7 +477,7 @@ _psref_held(const struct psref_target *target, struct psref_class *class, pcpu = percpu_getref(class->prc_percpu); /* Search through all the references on this CPU. */ - LIST_FOREACH(psref, &pcpu->pcpu_head, psref_entry) { + SLIST_FOREACH(psref, &pcpu->pcpu_head, psref_entry) { /* Sanity-check the reference's CPU. */ KASSERTMSG((psref->psref_cpu == curcpu()), "passive reference transferred from CPU %u to CPU %u", diff --git a/sys/sys/psref.h b/sys/sys/psref.h index 88db6dbb603..9096a3798d6 100644 --- a/sys/sys/psref.h +++ b/sys/sys/psref.h @@ -69,7 +69,7 @@ struct psref_target { * written only on the local CPU. */ struct psref { - LIST_ENTRY(psref) psref_entry; + SLIST_ENTRY(psref) psref_entry; const struct psref_target *psref_target; struct lwp *psref_lwp; struct cpu_info *psref_cpu; ==================== Of course, we also think this bug must be fixed before netbsd-8 rc. Thanks, -- ////////////////////////////////////////////////////////////////////// Internet Initiative Japan Inc. Device Engineering Section, IoT Platform Development Department, Network Division, Technology Unit Kengo NAKAHARA <k-nakah...@iij.ad.jp>