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netmap: don't schedule kqueue notify task when kqueue is not used
This change adds a counter (kqueue_users) to keep track of how many kqueue users are referencing a given struct nm_selinfo. In this way, nm_os_selwakeup() can schedule the kevent notification task only when kqueue is actually being used. This is important to avoid wasting CPU in the common case where kqueue is not used. Reviewed by: Aleksandr Fedorov <aleksandr.fedorov@itglobal.com> MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D19177
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19a227ee35
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45100257c6
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=344253
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@ -105,6 +105,7 @@ int nm_os_selinfo_init(NM_SELINFO_T *si, const char *name) {
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snprintf(si->mtxname, sizeof(si->mtxname), "nmkl%s", name);
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mtx_init(&si->m, si->mtxname, NULL, MTX_DEF);
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knlist_init_mtx(&si->si.si_note, &si->m);
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si->kqueue_users = 0;
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return (0);
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}
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@ -1351,7 +1352,9 @@ void
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nm_os_selwakeup(struct nm_selinfo *si)
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{
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selwakeuppri(&si->si, PI_NET);
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taskqueue_enqueue(si->ntfytq, &si->ntfytask);
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if (si->kqueue_users > 0) {
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taskqueue_enqueue(si->ntfytq, &si->ntfytask);
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}
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}
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void
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@ -1364,20 +1367,28 @@ static void
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netmap_knrdetach(struct knote *kn)
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{
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struct netmap_priv_d *priv = (struct netmap_priv_d *)kn->kn_hook;
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struct selinfo *si = &priv->np_si[NR_RX]->si;
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struct nm_selinfo *si = priv->np_si[NR_RX];
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nm_prinf("remove selinfo %p", si);
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knlist_remove(&si->si_note, kn, /*islocked=*/0);
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knlist_remove(&si->si.si_note, kn, /*islocked=*/0);
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NMG_LOCK();
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KASSERT(si->kqueue_users > 0, ("kqueue_user underflow on %s",
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si->mtxname));
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si->kqueue_users--;
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nm_prinf("kqueue users for %s: %d", si->mtxname, si->kqueue_users);
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NMG_UNLOCK();
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}
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static void
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netmap_knwdetach(struct knote *kn)
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{
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struct netmap_priv_d *priv = (struct netmap_priv_d *)kn->kn_hook;
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struct selinfo *si = &priv->np_si[NR_TX]->si;
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struct nm_selinfo *si = priv->np_si[NR_TX];
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nm_prinf("remove selinfo %p", si);
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knlist_remove(&si->si_note, kn, /*islocked=*/0);
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knlist_remove(&si->si.si_note, kn, /*islocked=*/0);
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NMG_LOCK();
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si->kqueue_users--;
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nm_prinf("kqueue users for %s: %d", si->mtxname, si->kqueue_users);
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NMG_UNLOCK();
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}
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/*
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@ -1465,6 +1476,10 @@ netmap_kqfilter(struct cdev *dev, struct knote *kn)
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kn->kn_fop = (ev == EVFILT_WRITE) ?
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&netmap_wfiltops : &netmap_rfiltops;
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kn->kn_hook = priv;
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NMG_LOCK();
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si->kqueue_users++;
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nm_prinf("kqueue users for %s: %d", si->mtxname, si->kqueue_users);
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NMG_UNLOCK();
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knlist_add(&si->si.si_note, kn, /*islocked=*/0);
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return 0;
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@ -132,11 +132,14 @@ struct netmap_adapter *netmap_getna(if_t ifp);
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#define MBUF_QUEUED(m) 1
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struct nm_selinfo {
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/* Support for select(2) and poll(2). */
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struct selinfo si;
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/* Support for kqueue(9). See comments in netmap_freebsd.c */
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struct taskqueue *ntfytq;
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struct task ntfytask;
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struct mtx m;
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char mtxname[32];
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int kqueue_users;
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};
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