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Update sendfile.2 to include a TUNING section that documents the

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various tunables that are applicable to sendfile(2).  Update tuning.7
to mention a reference to sendfile.2.

Approved by:	keramida
This commit is contained in:
Sean Chittenden 2003-03-12 09:28:44 +00:00
parent 4d3f408cee
commit 99c24e2b2c
2 changed files with 43 additions and 0 deletions
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38
lib/libc/sys/sendfile.2
View File

@ -106,6 +106,43 @@ The
implementation of
.Fn sendfile
is "zero-copy", meaning that it has been optimized so that copying of the file data is avoided.
.Sh TUNING
Internally this system call uses a special
.Xr sendfile 2
buffer
.Pq Fa "struct sf_buf"
to handle sending file data to the client.
If the sending socket is
blocking and there are not enough sendfile buffers available,
.Xr sendfile 2
will block and report a state of
.Dq sfbufa .
If the sending socket is non-blocking and there are not enough
sendfile buffers available, the call will block and wait for the
necessary buffers to become available before finishing the call.
.Pp
The number of
.Fa sf_buf Ns 's
allocated should be proportional to the number of nmbclusters used to
send data to a client via
.Xr sendfile 2 .
Tune accordingly to avoid blocking!
Busy installations that make extensive use of
.Xr sendfile 2
may want to increase these values to be inline with their
.Ar kern.ipc.nmbclusters
.Pq see Xr tuning 7 for details .
.Pp
The number of
.Xr sendfile 2
buffers in use is determined at boot time by either the
.Em kern.ipc.nsfbufs
.Xr loader.conf 5
variable or the
.Em NSFBUFS
kernel configuration tunable.
The number of sendfile buffers scales with
.Em kern.maxusers .
.Sh RETURN VALUES
.Rv -std sendfile
.Sh ERRORS
@ -161,6 +198,7 @@ If specified, the number of bytes successfully sent will be returned in
.Xr open 2 ,
.Xr send 2 ,
.Xr socket 2 ,
.Xr tuning 7 ,
.Xr writev 2
.Sh HISTORY
The

5
share/man/man7/tuning.7
View File

@ -775,6 +775,11 @@ with
.Va kern.maxusers
so you should not need to modify this parameter except under extreme
circumstances.
See the
.Dq TUNING
section in the
.Xr sendfile 2
man page for details.
.Sh KERNEL CONFIG TUNING
There are a number of kernel options that you may have to fiddle with in
a large-scale system.