Both issues caused the page daemon to erroneously go to sleep when
applications are consuming free pages at a high rate, leaving the
application threads blocked in VM_WAIT.
1) After completing an inactive queue scan, concurrent allocations may
have prevented the page daemon from meeting the v_free_min threshold.
In this case, the page daemon was going to sleep even when the
inactive queue contained plenty of clean pages.
2) pagedaemon_wakeup() may be called without the free queues lock held.
This can lead to a lost wakeup if a call occurs after the page daemon
clears vm_pageout_wanted but before going to sleep.
Fix 1) by ensuring that we start a new inactive queue scan immediately
if v_free_count < v_free_min after a prior scan.
Fix 2) by adding a new subroutine, pagedaemon_wait(), called from
vm_wait() and vm_waitpfault(). It wakes up the page daemon if either
vm_pages_needed or vm_pageout_wanted is false, and atomically sleeps
on v_free_count.
Reported by: jeff
Reviewed by: alc
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D13424
Latest clang git has a warning -Wnull-pointer-arithmetic which will
trigger a -Werror failure. Addition and subtraction from a null pointer
is undefined behaviour and could be optimized into anything.
Furthermore, using the difference between two pointers and casting the
result back to a pointer is not portable since the size of ptrdiff_t
does not necessary have to be the same as size of void* (this happens
e.g. on CHERI). Using intptr_t instead fixes this portability issue and
the compiler warning.
Submitted by; Alexander Richardson
Obtained from: CheriBSD
Differential Revision: https://reviews.freebsd.org/D12928
MFC after: 3 days
This squashes the warning gebnerated by GCC 6.x. Since
variables that are now removed had come documentation
value, put relevant bits in comment, so they can be
resurrected from there when actually needed.
new clang 6.0.0 -Wtautological-constant-compare warning to the WARNS <=
6 level. (This warning is still being worked on upstream to reduce
false positives, but it is currently still too trigger happy.)
being removed from GENERIC in 12. Always print PNP info for ISA when
it exists: it doesn't depend on ISAPNP. Add PNP ID to orm and vga to
prevent us from warning about them since those devices aren't being
removed from GENERIC. PNP devices will be removed from GENERIC too,
but they will be automatically loaded, so need no warning. We don't
warn for non-GENERIC kernels because people running them are presumed
to know what they are doing.
MFC After: 2 weeks
The daemonfd function is equivalent to the daemon(3) function expect that
arguments are descriptors. For example dhclient(8) which is sandboxed is
unable to open /dev/null to close stdio instead it's allows to fail
daemon(3) function to close the descriptors and then do it explicit in code.
Instead of such hacks we can use now daemonfd.
This API can be also helpful to migrate system to platforms like CheriBSD.
Reviewed by: brooks@, bcr@, jilles@ (earlier version)
Differential Revision: https://reviews.freebsd.org/D13433
clang does not know that two lookup calls will return the same
pointer, so it assumes correctly that using the old pointer
after dropping the reference to it is a bit risky.
Sometimes caller is only interested in how many clones
are there and NULL pointer is passed for the destination
buffer. Do not pass it to copyout then.
if_clone_attach function will drop the reference on failure which will
free the if_clone structure. No need to do it second time.
Reviewed by: glebius, ae
Differential Revision: https://reviews.freebsd.org/D10386
