CVS log for src/sys/sys/vmem_impl.h

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Add the notion of "private boundary tags" to vmem.  This allows vmem to
be used VERY early in boot; such consumers statically allocate the vmem
arena and boundary tags, and then explicitly add those static, private
boundary tags to the arena tag free list using the new function vmem_add_bts().

Vmem arenas that use private boundary tags will NOT consume the statically
allocated bootstrap tags used by the vmem system itself; the assumption is
that the consumer of such an arena knows what they're doing, and is responsible
for all necessary resource management.  A macro, VMEM_EST_BTCOUNT(), is
provided to help such consumers size the static boundary tag store based
on the expected number of spans and early allocations.  Once the private
tags are exhausted, the arena will dynamically allocate tags as usual.

Split the boundary tag "type" field into "type" and "flags" fields.
Initialize the flags field to 0 before inserting into an arena's free
tag list.

NFC, but makes diff for a future enhancement smaller.

vmem_init() requires the caller to include <sys/vmem_impl.h> in order
to know the storage size of "struct vmem", so put the prototype for
vmem_init() there as well.

Explicitly include <sys/pool.h> here; don't rely on it being included
by the includer.

Sync with HEAD

Sync with HEAD

- Fix uneven performance with "bursty" vmem arenas.  Adjust locking so that
  the mutex is acquired and released only once in the happy path.  Align
  tags to cachelines.  Size the hash table according to the maximum count of
  boundary tags over the interval just gone, not the instantaneous count,
  and decay that maximum value by 50%+1 after each rehash.  Round up to the
  next power of two to eliminate divisions.  Do the rehash check unlocked.

- Hash bucket size is sizeof(vmem_hashlist), not size of a pointer to same.

Rebase to HEAD as of a few days ago.

sync with head.

for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.

this commit was splitted into small chunks to avoid
a limitation of cvs.  ("Protocol error: too many arguments")

sync with head

file vmem_impl.h was added on branch yamt-pagecache on 2014-05-22 11:41:18 +0000

convert vmem, signals, powerhooks from CIRCLEQ -> TAILQ.

resync with head

file vmem_impl.h was added on branch tls-maxphys on 2013-02-25 00:30:13 +0000

make vmem(9) ready to be used early during bootstrap to replace extent(9)
pass memory for vmem structs into the initialization function and
do away with the static pool of vmem structs.
remove special bootstrapping of the quantum cache pools of the kmem_va_arena
as memory for pool_caches is allocated via pool_allocator_meta which is
fully operational at this point.

make vmem(9) ready to be used early during bootstrap to replace extent(9).
pass memory for vmem structs into the initialization functions and
do away with the static pools for this.
factor out the vmem internal structures into a private header.
remove special bootstrapping of the kmem_va_arena as all necessary memory
comes from pool_allocator_meta wich is fully operational at this point.