kernel.
When access restrictions are added to a page table entry, we flush the
corresponding virtual address mapping from the TLB. In contrast, when
access restrictions are removed from a page table entry, we do not
flush the virtual address mapping from the TLB. This is exactly as
recommended in AMD's documentation. In effect, when access
restrictions are removed from a page table entry, AMD's MMUs will
transparently refresh a stale TLB entry. In short, this saves us from
having to perform potentially costly TLB flushes. In contrast,
Intel's MMUs are allowed to generate a spurious page fault based upon
the stale TLB entry. Usually, such spurious page faults are handled
by vm_fault() without incident. However, when we are executing
no-fault sections of the kernel, we are not allowed to execute
vm_fault(). This change introduces special-case handling for spurious
page faults that occur in no-fault sections of the kernel.
In collaboration with: kib
Tested by: gibbs (an earlier version)
I would also like to acknowledge Hiroki Sato's assistance in
diagnosing this problem.
MFC after: 1 week
Add the sysctl debug.iosize_max_clamp, enabled by default. Setting the
sysctl to zero allows to perform the SSIZE_MAX-sized i/o requests from
the usermode.
Discussed with: bde, das (previous versions)
MFC after: 1 month
uiomove generates EFAULT if any accessed address is not mapped, as
opposed to handling the fault.
Sponsored by: The FreeBSD Foundation
Reviewed by: alc (previous version)
misnamed since it was introduced and should not be globally exposed
with this name. The equivalent functionality is now available using
kern_yield(curthread->td_user_pri). The function remains
undocumented.
Bump __FreeBSD_version.
- entirely eliminate some calls to uio_yeild() as being unnecessary,
such as in a sysctl handler.
- move should_yield() and maybe_yield() to kern_synch.c and move the
prototypes from sys/uio.h to sys/proc.h
- add a slightly more generic kern_yield() that can replace the
functionality of uio_yield().
- replace source uses of uio_yield() with the functional equivalent,
or in some cases do not change the thread priority when switching.
- fix a logic inversion bug in vlrureclaim(), pointed out by bde@.
- instead of using the per-cpu last switched ticks, use a per thread
variable for should_yield(). With PREEMPTION, the only reasonable
use of this is to determine if a lock has been held a long time and
relinquish it. Without PREEMPTION, this is essentially the same as
the per-cpu variable.
should_yield(). Use this in various places. Encapsulate the common
case of check-and-yield into a new function maybe_yield().
Change several checks for a magic number of iterations to use
should_yield() instead.
MFC after: 1 week
vm_page_try_to_free(). Consequently, push down the page queues lock into
pmap_enter_quick(), pmap_page_wired_mapped(), pmap_remove_all(), and
pmap_remove_write().
Push down the page queues lock into Xen's pmap_page_is_mapped(). (I
overlooked the Xen pmap in r207702.)
Switch to a per-processor counter for the total number of pages cached.
managed pages that didn't already have that lock held. (Freeing an
unmanaged page, such as the various pmaps use, doesn't require the page
lock.)
This allows a change in vm_page_remove()'s locking requirements. It now
expects the page lock to be held instead of the page queues lock.
Consequently, the page queues lock is no longer required at all by callers
to vm_page_rename().
Discussed with: kib
Although this file has historically been used as a dumping ground for
random functions, nowadays it only contains functions related to copying
bits {from,to} userspace and hash table utility functions.
Behold, subr_uio.c and subr_hash.c.
