netdev - Re: [PATCH net-next] Replace 2 jiffies with sysctl netdev_budget

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Message-Id: <20170421.160052.848351578908155648.davem@davemloft.net>
Date:   Fri, 21 Apr 2017 16:00:52 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     tedheadster@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] Replace 2 jiffies with sysctl
 netdev_budget_usecs to enable softirq tuning

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 21 Apr 2017 12:57:02 -0700

> On Fri, 2017-04-21 at 13:22 -0400, David Miller wrote:
>> From: Matthew Whitehead <tedheadster@...il.com>
>> Date: Wed, 19 Apr 2017 12:37:10 -0400
>> 
>> > Constants used for tuning are generally a bad idea, especially as hardware
>> > changes over time. Replace the constant 2 jiffies with sysctl variable
>> > netdev_budget_usecs to enable sysadmins to tune the softirq processing.
>> > Also document the variable.
>> > 
>> > For example, a very fast machine might tune this to 1000 microseconds,
>> > while my regression testing 486DX-25 needs it to be 4000 microseconds on
>> > a nearly idle network to prevent time_squeeze from being incremented.
>> > 
>> > Version 2: changed jiffies to microseconds for predictable units.
>> > 
>> > Signed-off-by: Matthew Whitehead <tedheadster@...il.com>
>> 
>> Applied, thanks.
> 
> Can we revert the changes in kernel/sysctl_binary.c &
> include/uapi/linux/sysctl.h ?
> 
> { CTL_INT,      NET_CORE_BUDGET_USECS,  "netdev_budget_usecs" },
> 
> NET_CORE_BUDGET_USECS=23,
> 
> Unless I am missing something, we should not add new binary sysctls.

That's true, I'll kill this.

====================
[PATCH] net: Remove NET_CORE_BUDGET_USECS from sysctl binary interface.

We are not supposed to add new entries to this thing
any more.

Thanks to Eric Dumazet for noticing this.

Signed-off-by: David S. Miller <davem@...emloft.net>
---
 include/uapi/linux/sysctl.h | 1 -
 kernel/sysctl_binary.c      | 1 -
 2 files changed, 2 deletions(-)

diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index 177f5f1..e13d480 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -274,7 +274,6 @@ enum
 	NET_CORE_AEVENT_ETIME=20,
 	NET_CORE_AEVENT_RSEQTH=21,
 	NET_CORE_WARNINGS=22,
-	NET_CORE_BUDGET_USECS=23,
 };
 
 /* /proc/sys/net/ethernet */
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 4ee3e49..ece4b17 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -197,7 +197,6 @@ static const struct bin_table bin_net_core_table[] = {
 	{ CTL_INT,	NET_CORE_AEVENT_ETIME,	"xfrm_aevent_etime" },
 	{ CTL_INT,	NET_CORE_AEVENT_RSEQTH,	"xfrm_aevent_rseqth" },
 	{ CTL_INT,	NET_CORE_WARNINGS,	"warnings" },
-	{ CTL_INT,	NET_CORE_BUDGET_USECS,	"netdev_budget_usecs" },
 	{},
 };
 
-- 
2.4.11