diff options
Diffstat (limited to 'share')
-rw-r--r-- | share/man/man4/polling.4 | 43 |
1 files changed, 21 insertions, 22 deletions
diff --git a/share/man/man4/polling.4 b/share/man/man4/polling.4 index 450a610..a8cbd19 100644 --- a/share/man/man4/polling.4 +++ b/share/man/man4/polling.4 @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd March 26, 2005 +.Dd October 1, 2005 .Dt POLLING 4 .Os .Sh NAME @@ -32,7 +32,6 @@ .Nd device polling support .Sh SYNOPSIS .Cd "options DEVICE_POLLING" -.Cd "options HZ=1000" .Sh DESCRIPTION Device polling .Nm ( @@ -69,7 +68,7 @@ persistently processing interrupts without being able to complete other work, either in the kernel or in userland. .Pp Device polling disables interrupts by polling devices at appropriate -times, i.e., on clock interrupts, system calls and within the idle loop. +times, i.e., on clock interrupts and within the idle loop. This way, the context switch overhead is removed. Furthermore, the operating system can control accurately how much work to spend @@ -81,6 +80,13 @@ Enabling also changes the way software network interrupts are scheduled, so there is never the risk of livelock because packets are not processed to completion. +.Ss Enabling polling +Currently only network interface drivers support the +.Nm +feature. +It is turned on and off with help of +.Xr ifconfig 8 +command. .Ss MIB Variables The operation of .Nm @@ -89,11 +95,6 @@ is controlled by the following MIB variables: .Pp .Bl -tag -width indent -compact -.It Va kern.polling.enable -If set to non-zero, -.Nm -is enabled. -Default is disabled. .Pp .It Va kern.polling.user_frac When @@ -142,16 +143,6 @@ Controls if is enabled in the idle loop. There are no reasons (other than power saving or bugs in the scheduler's handling of idle priority kernel threads) to disable this. -Note that -CURRENT apparently has some problems in this respect now, -so default is disabled. -.Pp -.It Va kern.polling.poll_in_trap -Controls if -.Nm -is enabled during hardware traps. -Enabling this can be useful to improve the network responsiveness -of boxes with 100% CPU usage. -Default is disabled. .Pp .It Va kern.polling.reg_frac Controls how often (every @@ -166,6 +157,15 @@ Default is 20. How many active devices have registered for .Nm . .Pp +.It Va kern.polling.enable +Legacy MIB, that was used to enable or disable polling globally. +Currently if set to 1, +.Nm +is enabled on all capable interfaces. +If set to 0, +.Nm +is disabled on all interfaces. +.Pp .It Va kern.polling.short_ticks .It Va kern.polling.lost_polls .It Va kern.polling.pending_polls @@ -205,10 +205,9 @@ to probe the device for events and process them. conditionally compiled sections of the devices mentioned above for more details.) .Pp -As in the worst case the devices are only polled on -clock interrupts, in order to reduce the latency in processing -packets, it is advisable to increase the frequency of the clock -to at least 1000 HZ. +As in the worst case the devices are only polled on clock interrupts, +in order to reduce the latency in processing packets, it is advisable +do not to decrease the frequency of the clock below 1000 Hz. .Sh HISTORY Device polling first appeared in .Fx 4.6 |