them as ints. Among other bugs, doing so at best caused benign
overflow followed by fatal sign extension on machines with 32-bit
ints and 64-bit longs.
writes of size (100,208]+N*MCLBYTES.
The bug:
sosend() hands each mbuf off to the protocol output routine as soon as it
has copied it, in the hopes of increasing parallelism (see
http://www.kohala.com/~rstevens/vanj.88jul20.txt ). This works well for
TCP as long as the first mbuf handed off is at least the MSS. However,
when doing small writes (between MHLEN and MINCLSIZE), the transaction is
split into 2 small MBUF's and each is individually handed off to TCP.
TCP assumes that the first small mbuf is the whole transaction, so sends
a small packet. When the second small mbuf arrives, Nagle prevents TCP
from sending it so it must wait for a (potentially delayed) ACK. This
sends throughput down the toilet.
The workaround:
Set the "atomic" flag when we're doing small writes. The "atomic" flag
has two meanings:
1. Copy all of the data into a chain of mbufs before handing off to the
protocol.
2. Leave room for a datagram header in said mbuf chain.
TCP wants the first but doesn't want the second. However, the second
simply results in some memory wastage (but is why the workaround is a
hack and not a fix).
The real fix:
The real fix for this problem is to introduce something like a "requested
transfer size" variable in the socket->protocol interface. sosend()
would then accumulate an mbuf chain until it exceeded the "requested
transfer size". TCP could set it to the TCP MSS (note that the
current interface causes strange TCP behaviors when the MSS > MCLBYTES;
nobody notices because MCLBYTES > ethernet's MTU).
is the kernel part of my commits, the userlevel stuff will be done in
a separate commit. Add the ability to suspend as well as hibernate to
syscons. Create a new virtual key like hibernate for suspend. Update
apm_bios.h to define more apm bios goodies.
Any packet that can be matched by a ipfw rule can be redirected
transparently to another port or machine. Redirection to another port
mostly makes sense with tcp, where a session can be set up
between a proxy and an unsuspecting client. Redirection to another machine
requires that the other machine also be expecting to receive the forwarded
packets, as their headers will not have been modified.
/sbin/ipfw must be recompiled!!!
Reviewed by: Peter Wemm <peter@freebsd.org>
Submitted by: Chrisy Luke <chrisy@flix.net>
Each devfs node has (and has had fro a while) a pointer directly to
the correct cdefsw entry so just use it instead of doing the lookup.
There are several other places in the kernel that still use the tables
however, so they can't go away yet..
Not sure of the result of it..
(may or may not effect anything) but it's fixed now.
(found by: comparing what cvsup sent back to me with what I tested..)
mask address around when registering interrupts is wrong IMHO. We should
use a priority level like IPL_BIO and the lower levels can then translate
it into a mask if they want.
There is only cdevsw (which should be renamed in a later edit to deventry
or something). cdevsw contains the union of what were in both bdevsw an
cdevsw entries. The bdevsw[] table stiff exists and is a second pointer
to the cdevsw entry of the device. it's major is in d_bmaj rather than
d_maj. some cleanup still to happen (e.g. dsopen now gets two pointers
to the same cdevsw struct instead of one to a bdevsw and one to a cdevsw).
rawread()/rawwrite() went away as part of this though it's not strictly
the same patch, just that it involves all the same lines in the drivers.
cdroms no longer have write() entries (they did have rawwrite (?)).
tapes no longer have support for bdev operations.
Reviewed by: Eivind Eklund and Mike Smith
Changes suggested by eivind.
