The tunable vfs.devfs.fops controls this feature and defaults to off.
When enabled (vfs.devfs.fops=1 in loader), device vnodes opened
through a filedescriptor gets a special fops vector which instead
of the detour through the vnode layer goes directly to DEVFS.
Amongst other things this allows us to run Giant free read/write to
device drivers which have been weaned off D_NEEDGIANT.
Currently this means /dev/null, /dev/zero, disks, (and maybe the
random stuff ?)
On a 700MHz K7 machine this doubles the speed of
dd if=/dev/zero of=/dev/null bs=1 count=1000000
This roughly translates to shaving 2usec of each read/write syscall.
The poll/kqfilter paths need more work before they are giant free,
this work is ongoing in p4::phk_bufwork
Please test this and report any problems, LORs etc.
Change the spelling of the "catch" option to be consistent with the new
options. Implement the "no wait" option. An implementation of the "CPU
private" for i386 will be committed at a later date.
This generates a KTR event for each critical section entered and exited.
It would be desirable to also log the filename and line number of the
source entering or exiting the critical section, but this requires
hacking up the critical section API, so I've not done that yet.
retain the pcbinfo lock until we're done using a pcb in the in-bound
path, as the pcbinfo lock acts as a pseuo-reference to prevent the pcb
from potentially being recycled. Clean up assertions and make sure to
assert that the pcbinfo is locked at the head of code subsections where
it is needed. Free the mbuf at the end of tcp_input after releasing
any held locks to reduce the time the locks are held.
MFC after: 3 weeks
number of entries into bucket_zone_lookup(), which helps make more
clear the logic of consumers of bucket zones.
Annotate the behavior of bucket_init() with a comment indicating
how the various data structures, including the bucket lookup tables,
are initialized.
swapoff: failed to locate %d swap blocks
The race occurred because putpages() can block between the time it
allocates swap space and the time it updates the swap metadata to
associate that space with a vm_object, so swapoff() would complain
about the temporary inconsistency. I hoped to fix this by making
swp_pager_getswapspace() and swp_pager_meta_build() a single atomic
operation, but that proved to be inconvenient. With this change,
swapoff() simply doesn't attempt to be so clever about detecting when
all the pageout activity to the target device should have drained.
because this call is only needed to wake threads that slept when they
discovered a dead object connected to a vnode. To eliminate unnecessary
calls to wakeup() by vnode_pager_dealloc(), introduce a new flag,
OBJ_DISCONNECTWNT.
Reviewed by: tegge@
Expose some of the amd64-specific sysarch functions to allow alternative
implementations of the %fs/%gs code for TLS, threads, etc. USER_LDT does
not exist on the amd64 kernel, so we have to implement things other ways.
priority. The sleep queues don't get updated when the priority of
threads changes, so sleepq_signal() might not always wakeup the
highest priority thread. Updating the queues when thread priorities
change cannot be easily done due to lock orders, so instead we do an
O(n) walk of the queue for a sleepq_signal() operation instead of O(1).
On the other hand, adding a thread to a sleep queue now goes from O(n)
to O(1) so it ends up as an even tradeoff. The correctness here with
regards to priorities is actually fairly important. msleep() gives
interactive threads their priority "boost" after they are placed on the
queue, but before this fix that "boost" wasn't used to determine the
highest priority thread that sleepq_signal() awoke.
- Fix up some comments.
Inspired by: ups, bde
