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Replace 2 jiffies with sysctl netdev_budget_usecs to enable softirq tuning

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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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Matthew Whitehead
2017-04-19 12:37:10 -04:00
committed by David S. Miller
parent 20da848f8e
commit 7acf8a1e8a
6 changed files with 24 additions and 2 deletions
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11
Documentation/sysctl/net.txt
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@@ -188,7 +188,16 @@ netdev_budget
Maximum number of packets taken from all interfaces in one polling cycle (NAPI
poll). In one polling cycle interfaces which are registered to polling are
probed in a round-robin manner.
probed in a round-robin manner. Also, a polling cycle may not exceed
netdev_budget_usecs microseconds, even if netdev_budget has not been
exhausted.
netdev_budget_usecs
---------------------
Maximum number of microseconds in one NAPI polling cycle. Polling
will exit when either netdev_budget_usecs have elapsed during the
poll cycle or the number of packets processed reaches netdev_budget.
netdev_max_backlog
------------------