[Differential] D24937: Add readonly tunable net.iflib.tx_update_freq to set transmit descriptor update frequency

[neel_neelc.org (Neel Chauhan)]

neel_neelc.org created this revision.
neel_neelc.org added a project: network.
Herald added subscribers: Contributor Reviews (base), melifaro, ae, imp.
Herald added a reviewer: shurd.
Herald added a reviewer: iflib.
neel_neelc.org requested review of this revision.

REVISION SUMMARY
  Introduce readonly tunable net.iflib.tx_update_freq to allow an user to set the network transmit descriptor update frequency. Previously, this was hardcoded at 16.
  
  Submitted by: Neel Chauhan <neel AT neelc DOT org>

TEST PLAN
  Add this to /boot/loader.conf:
  
  net.iflib.tx_update_freq=32
  
  Reboot to see if it works

REPOSITORY
  rS FreeBSD src repository

REVISION DETAIL
  https://reviews.freebsd.org/D24937

AFFECTED FILES
  sys/net/iflib.c

CHANGE DETAILS

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -586,8 +586,11 @@
 static int iflib_no_tx_batch = 0;
 SYSCTL_INT(_net_iflib, OID_AUTO, no_tx_batch, CTLFLAG_RW,
 		   &iflib_no_tx_batch, 0, "minimize transmit latency at the possible expense of throughput");
+static int iflib_tx_update_freq = IFLIB_DEFAULT_TX_UPDATE_FREQ;
+SYSCTL_UINT(_net_iflib, OID_AUTO, tx_update_freq, CTLFLAG_RDTUN,
+		   &iflib_tx_update_freq, IFLIB_DEFAULT_TX_UPDATE_FREQ,
+		   "tramsmit descriptor updates per second");
 
-
 #if IFLIB_DEBUG_COUNTERS
 
 static int iflib_tx_seen;
@@ -1762,8 +1765,7 @@
 
 	/* Set number of descriptors available */
 	txq->ift_qstatus = IFLIB_QUEUE_IDLE;
-	/* XXX make configurable */
-	txq->ift_update_freq = IFLIB_DEFAULT_TX_UPDATE_FREQ;
+	txq->ift_update_freq = iflib_tx_update_freq;
 
 	/* Reset indices */
 	txq->ift_cidx_processed = 0;



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To: neel_neelc.org, shurd, #iflib
Cc: imp, ae, melifaro, #contributor_reviews_base, freebsd-net-list, mmacy, kpraveen.lkml_gmail.com, marcnarc_gmail.com, simonvella_gmail.com, novice_techie.com, tommi.pernila_iki.fi, krzysztof.galazka_intel.com
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