git: c9021340a326 - main - e1000: Add sysctl for igb(4) DMA Coalesce

The branch main has been updated by kbowling:

URL: https://cgit.FreeBSD.org/src/commit/?id=c9021340a3266f924bf721182f14f2d265d8a82c

commit c9021340a3266f924bf721182f14f2d265d8a82c
Author:     Kevin Bowling <kbowling@FreeBSD.org>
AuthorDate: 2024-09-24 10:25:24 +0000
Commit:     Kevin Bowling <kbowling@FreeBSD.org>
CommitDate: 2024-09-24 10:47:05 +0000

    e1000: Add sysctl for igb(4) DMA Coalesce
    
    This feature can increase efficiency at the expense of latency
    
    It does not work well with the default interrupt delay, but expose
    the otherwise unconnected code in the driver in case people want to
    experiment.
    
    See
    https://www.intel.com/content/dam/support/us/en/documents/network/adapter/pro100/sb/466827_intel_r__dma_coalescing_white_paper_v003.pdf
    
    MFC after:      1 week
    Sponsored by:   Blue Box Systems
---
 sys/dev/e1000/if_em.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/sys/dev/e1000/if_em.c b/sys/dev/e1000/if_em.c
index d06627bcfda1..ad12171487f6 100644
--- a/sys/dev/e1000/if_em.c
+++ b/sys/dev/e1000/if_em.c
@@ -354,6 +354,7 @@ static void	em_enable_vectors_82574(if_ctx_t);
 
 static int	em_set_flowcntl(SYSCTL_HANDLER_ARGS);
 static int	em_sysctl_eee(SYSCTL_HANDLER_ARGS);
+static int	igb_sysctl_dmac(SYSCTL_HANDLER_ARGS);
 static void	em_if_led_func(if_ctx_t, int);
 
 static int	em_get_regs(SYSCTL_HANDLER_ARGS);
@@ -855,6 +856,12 @@ em_if_attach_pre(if_ctx_t ctx)
 	    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, sc, 0,
 	    em_get_rs, "I", "Dump RS indexes");
 
+	if (hw->mac.type >= e1000_i350) {
+		SYSCTL_ADD_PROC(ctx_list, child, OID_AUTO, "dmac",
+		    CTLTYPE_INT | CTLFLAG_RW, sc, 0,
+		    igb_sysctl_dmac, "I", "DMA Coalesce");
+	}
+
 	scctx->isc_tx_nsegments = EM_MAX_SCATTER;
 	scctx->isc_nrxqsets_max = scctx->isc_ntxqsets_max = em_set_num_queues(ctx);
 	if (bootverbose)
@@ -4973,6 +4980,55 @@ em_set_flowcntl(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
+/*
+ * Manage DMA Coalesce:
+ * Control values:
+ * 	0/1 - off/on
+ *	Legal timer values are:
+ *	250,500,1000-10000 in thousands
+ */
+static int
+igb_sysctl_dmac(SYSCTL_HANDLER_ARGS)
+{
+	struct e1000_softc *sc = (struct e1000_softc *) arg1;
+	int error;
+
+	error = sysctl_handle_int(oidp, &sc->dmac, 0, req);
+
+	if ((error) || (req->newptr == NULL))
+		return (error);
+
+	switch (sc->dmac) {
+		case 0:
+			/* Disabling */
+			break;
+		case 1: /* Just enable and use default */
+			sc->dmac = 1000;
+			break;
+		case 250:
+		case 500:
+		case 1000:
+		case 2000:
+		case 3000:
+		case 4000:
+		case 5000:
+		case 6000:
+		case 7000:
+		case 8000:
+		case 9000:
+		case 10000:
+			/* Legal values - allow */
+			break;
+		default:
+			/* Do nothing, illegal value */
+			sc->dmac = 0;
+			return (EINVAL);
+	}
+	/* Reinit the interface */
+	em_if_init(sc->ctx);
+	return (error);
+}
+
 /*
  * Manage Energy Efficient Ethernet:
  * Control values: