Module Name: src
Committed By: knakahara
Date: Fri Mar 24 10:02:35 UTC 2017
Modified Files:
src/sys/dev/pci: if_wm.c
Log Message:
add comments about the situation wm(4) use MSI-X but does not use multiqueue.
To generate a diff of this commit:
cvs rdiff -u -r1.502 -r1.503 src/sys/dev/pci/if_wm.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/pci/if_wm.c
diff -u src/sys/dev/pci/if_wm.c:1.502 src/sys/dev/pci/if_wm.c:1.503
--- src/sys/dev/pci/if_wm.c:1.502 Fri Mar 24 10:01:55 2017
+++ src/sys/dev/pci/if_wm.c Fri Mar 24 10:02:35 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: if_wm.c,v 1.502 2017/03/24 10:01:55 knakahara Exp $ */
+/* $NetBSD: if_wm.c,v 1.503 2017/03/24 10:02:35 knakahara Exp $ */
/*
* Copyright (c) 2001, 2002, 2003, 2004 Wasabi Systems, Inc.
@@ -84,7 +84,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.502 2017/03/24 10:01:55 knakahara Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wm.c,v 1.503 2017/03/24 10:02:35 knakahara Exp $");
#ifdef _KERNEL_OPT
#include "opt_net_mpsafe.h"
@@ -2561,10 +2561,21 @@ alloc_retry:
ifp->if_ioctl = wm_ioctl;
if ((sc->sc_flags & WM_F_NEWQUEUE) != 0) {
ifp->if_start = wm_nq_start;
+ /*
+ * When the number of CPUs is one and the controller can use
+ * MSII-X, wm(4) use MSI-X but *does not* use multiqueue.
+ * That is, wm(4) use two interrupts, one is used for Tx/Rx
+ * and the other is used for link status changing.
+ * In this situation, wm_nq_transmit() is disadvantageous
+ * because of wm_select_txqueue() and pcq(9) overhead.
+ */
if (wm_is_using_multiqueue(sc))
ifp->if_transmit = wm_nq_transmit;
} else {
ifp->if_start = wm_start;
+ /*
+ * wm_transmit() has the same disadvantage as wm_transmit().
+ */
if (wm_is_using_multiqueue(sc))
ifp->if_transmit = wm_transmit;
}
@@ -2833,7 +2844,7 @@ wm_watchdog(struct ifnet *ifp)
/*
* There are still some upper layer processing which call
- * ifp->if_start(). e.g. ALTQ
+ * ifp->if_start(). e.g. ALTQ or one CPU system
*/
/* Try to get more packets going. */
ifp->if_start(ifp);
@@ -7611,12 +7622,12 @@ wm_deferred_start_locked(struct wm_txque
}
if ((sc->sc_flags & WM_F_NEWQUEUE) != 0) {
- /* XXX need for ALTQ */
+ /* XXX need for ALTQ or one CPU system */
if (qid == 0)
wm_nq_start_locked(ifp);
wm_nq_transmit_locked(ifp, txq);
} else {
- /* XXX need for ALTQ */
+ /* XXX need for ALTQ or one CPU system */
if (qid == 0)
wm_start_locked(ifp);
wm_transmit_locked(ifp, txq);
