Date: Fri, 24 Jan 2020 10:24:53 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Gleb Smirnoff <glebius@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r357004 - in head/sys: kern sys Message-ID: <23f272a4-c997-a454-19d6-10392713e71f@selasky.org> In-Reply-To: <fb6e84b6-85a9-3252-c27a-bb9ee7ca203f@selasky.org> References: <202001230124.00N1OlXi029506@repo.freebsd.org> <fb6e84b6-85a9-3252-c27a-bb9ee7ca203f@selasky.org>
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On 2020-01-23 09:36, Hans Petter Selasky wrote: > On 2020-01-23 02:24, Gleb Smirnoff wrote: >> Author: glebius >> Date: Thu Jan 23 01:24:47 2020 >> New Revision: 357004 >> URL: https://svnweb.freebsd.org/changeset/base/357004 >> >> Log: >> Enter the network epoch for interrupt handlers of INTR_TYPE_NET. >> Provide tunable to limit how many times handlers may be executed >> without reentering epoch. >> Differential Revision: https://reviews.freebsd.org/D23242 >> >> Modified: >> head/sys/kern/kern_intr.c >> head/sys/sys/interrupt.h >> >> Modified: head/sys/kern/kern_intr.c >> ============================================================================== >> >> --- head/sys/kern/kern_intr.c Thu Jan 23 01:20:59 2020 (r357003) >> +++ head/sys/kern/kern_intr.c Thu Jan 23 01:24:47 2020 (r357004) >> @@ -48,6 +48,7 @@ __FBSDID("$FreeBSD$"); >> #include <sys/mutex.h> >> #include <sys/priv.h> >> #include <sys/proc.h> >> +#include <sys/epoch.h> >> #include <sys/random.h> >> #include <sys/resourcevar.h> >> #include <sys/sched.h> >> @@ -94,6 +95,9 @@ static int intr_storm_threshold = 0; >> SYSCTL_INT(_hw, OID_AUTO, intr_storm_threshold, CTLFLAG_RWTUN, >> &intr_storm_threshold, 0, >> "Number of consecutive interrupts before storm protection is >> enabled"); >> +static int intr_epoch_batch = 1000; >> +SYSCTL_INT(_hw, OID_AUTO, intr_epoch_batch, CTLFLAG_RWTUN, >> &intr_epoch_batch, >> + 0, "Maximum interrupt handler executions without re-entering >> epoch(9)"); >> static TAILQ_HEAD(, intr_event) event_list = >> TAILQ_HEAD_INITIALIZER(event_list); >> static struct mtx event_lock; >> @@ -587,6 +591,8 @@ intr_event_add_handler(struct intr_event *ie, >> const ch >> ih->ih_flags |= IH_MPSAFE; >> if (flags & INTR_ENTROPY) >> ih->ih_flags |= IH_ENTROPY; >> + if (flags & INTR_TYPE_NET) >> + ih->ih_flags |= IH_NET; >> /* We can only have one exclusive handler in a event. */ >> mtx_lock(&ie->ie_lock); >> @@ -1196,11 +1202,12 @@ ithread_execute_handlers(struct proc *p, >> struct intr_e >> static void >> ithread_loop(void *arg) >> { >> + struct epoch_tracker et; >> struct intr_thread *ithd; >> struct intr_event *ie; >> struct thread *td; >> struct proc *p; >> - int wake; >> + int wake, epoch_count; >> td = curthread; >> p = td->td_proc; >> @@ -1235,8 +1242,21 @@ ithread_loop(void *arg) >> * that the load of ih_need in ithread_execute_handlers() >> * is ordered after the load of it_need here. >> */ >> - while (atomic_cmpset_acq_int(&ithd->it_need, 1, 0) != 0) >> + if (ie->ie_hflags & IH_NET) { >> + epoch_count = 0; >> + NET_EPOCH_ENTER(et); >> + } >> + while (atomic_cmpset_acq_int(&ithd->it_need, 1, 0) != 0) { >> ithread_execute_handlers(p, ie); >> + if ((ie->ie_hflags & IH_NET) && >> + ++epoch_count >= intr_epoch_batch) { >> + NET_EPOCH_EXIT(et); >> + epoch_count = 0; >> + NET_EPOCH_ENTER(et); >> + } >> + } >> + if (ie->ie_hflags & IH_NET) >> + NET_EPOCH_EXIT(et); >> WITNESS_WARN(WARN_PANIC, NULL, "suspending ithread"); >> mtx_assert(&Giant, MA_NOTOWNED); Hi Gleb, What you want to do here is right, but how it is implemented is wrong, in my opinion. 1) Remove intr_epoch_batch. Most network drivers use interrupt moderation, and a timeout of 1000 iterations can easily become 1 second under heavly load ! 2) You need to make a new request function for interrupts which take a pointer to an EPOCH and replace that IH_NET in hflags! --HPS
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