Commit Graph

19 Commits

Author SHA1 Message Date
Alan Cox
703b304f33 Eliminate a redundant parameter to vm_radix_replace().
Improve the wording of the comment describing vm_radix_replace().

Reviewed by:	attilio
MFC after:	6 weeks
Sponsored by:	EMC / Isilon Storage Division
2013-12-08 20:07:02 +00:00
Alan Cox
776cad90ff Addendum to r254141: The call to vm_radix_insert() in vm_page_cache() can
reclaim the last preexisting cached page in the object, resulting in a call
to vdrop().  Detect this scenario so that the vnode's hold count is
correctly maintained.  Otherwise, we panic.

Reported by:	scottl
Tested by:	pho
Discussed with:	attilio, jeff, kib
2013-08-23 17:27:12 +00:00
Attilio Rao
e946b94934 On all the architectures, avoid to preallocate the physical memory
for nodes used in vm_radix.
On architectures supporting direct mapping, also avoid to pre-allocate
the KVA for such nodes.

In order to do so make the operations derived from vm_radix_insert()
to fail and handle all the deriving failure of those.

vm_radix-wise introduce a new function called vm_radix_replace(),
which can replace a leaf node, already present, with a new one,
and take into account the possibility, during vm_radix_insert()
allocation, that the operations on the radix trie can recurse.
This means that if operations in vm_radix_insert() recursed
vm_radix_insert() will start from scratch again.

Sponsored by:	EMC / Isilon storage division
Reviewed by:	alc (older version)
Reviewed by:	jeff
Tested by:	pho, scottl
2013-08-09 11:28:55 +00:00
Alan Cox
9f2e600890 To reduce the amount of arithmetic performed in the various radix tree
functions, reverse the numbering scheme for the levels.  The highest
numbered level in the tree now appears near the root instead of the leaves.

Sponsored by:	EMC / Isilon Storage Division
2013-05-11 18:01:41 +00:00
Alan Cox
bb0e1de4ab Remove a redundant call to panic() from vm_radix_keydiff(). The assertion
before the loop accomplishes the same thing.

Sponsored by:	EMC / Isilon Storage Division
2013-05-07 18:45:34 +00:00
Alan Cox
2d4b9a6438 Optimize vm_radix_lookup_ge() and vm_radix_lookup_le(). Specifically,
change the way that these functions ascend the tree when the search for a
matching leaf fails at an interior node.  Rather than returning to the root
of the tree and repeating the lookup with an updated key, maintain a stack
of interior nodes that were visited during the descent and use that stack
to resume the lookup at the closest ancestor that might have a matching
descendant.

Sponsored by:	EMC / Isilon Storage Division
Reviewed by:	attilio
Tested by:	pho
2013-05-04 22:50:15 +00:00
Alan Cox
82af926a57 Eliminate an unneeded call to vm_radix_trimkey() from vm_radix_lookup_le().
This call is clearing bits from the key that will be set again by the next
line.

Sponsored by:	EMC / Isilon Storage Division
2013-04-28 08:29:00 +00:00
Alan Cox
40076ebc5c Avoid some lookup restarts in vm_radix_lookup_{ge,le}().
Sponsored by:	EMC / Isilon Storage Division
2013-04-27 16:44:59 +00:00
Alan Cox
384875a3a6 Simplify vm_radix_{add,dec}lev().
Sponsored by:	EMC / Isilon Storage Division
2013-04-22 01:26:13 +00:00
Alan Cox
880659fe81 When calculating the number of reserved nodes, discount the pages that will
be used to store the nodes.

Sponsored by:	EMC / Isilon Storage Division
2013-04-18 05:34:33 +00:00
Alan Cox
a08f2cf69e Although we perform path compression to reduce the height of the trie and
the number of interior nodes, we have previously created a level zero
interior node at the root of every non-empty trie, even when that node is
not strictly necessary, i.e., it has only one child.  This change is the
second (and final) step in eliminating those unnecessary level zero interior
nodes.  Specifically, it updates the deletion and insertion functions so
that they do not require a level zero interior node at the root of the trie.
For a "buildworld" workload, this change results in a 16.8% reduction in the
number of interior nodes allocated and a similar reduction in the average
execution time for lookup functions.  For example, the average execution
time for a call to vm_radix_lookup_ge() is reduced by 22.9%.

Reviewed by:	attilio, jeff (an earlier version)
Sponsored by:	EMC / Isilon Storage Division
2013-04-15 06:12:00 +00:00
Alan Cox
6f9c0b15bb Although we perform path compression to reduce the height of the trie and
the number of interior nodes, we always create a level zero interior node at
the root of every non-empty trie, even when that node is not strictly
necessary, i.e., it has only one child.  This change is the first step in
eliminating those unnecessary level zero interior nodes.  Specifically, it
updates all of the lookup functions so that they do not require a level zero
interior node at the root.

Reviewed by:	attilio, jeff (an earlier version)
Sponsored by:	EMC / Isilon Storage Division
2013-04-12 20:21:28 +00:00
Alan Cox
2c899fede2 Micro-optimize the order of struct vm_radix_node's fields. Specifically,
arrange for all of the fields to start at a short offset from the
beginning of the structure.

Eliminate unnecessary masking of VM_RADIX_FLAGS from the root pointer in
vm_radix_getroot().

Sponsored by:	EMC / Isilon Storage Division
2013-04-07 01:30:51 +00:00
Alan Cox
c1c82b36ad Simplify vm_radix_keybarr().
Sponsored by:	EMC / Isilon Storage Division
2013-04-06 18:04:35 +00:00
Alan Cox
72abda6466 Simplify vm_radix_insert().
Reviewed by:	attilio
Tested by:	pho
Sponsored by:	EMC / Isilon Storage Division
2013-04-06 06:02:55 +00:00
Alan Cox
96f1a84272 Replace the remaining uses of vm_radix_node_page() by vm_radix_isleaf() and
vm_radix_topage().  This transformation eliminates some unnecessary
conditional branches from the inner loops of vm_radix_insert(),
vm_radix_lookup{,_ge,_le}(), and vm_radix_remove().

Simplify the control flow of vm_radix_lookup_{ge,le}().

Reviewed by:	attilio (an earlier version)
Tested by:	pho
Sponsored by:	EMC / Isilon Storage Division
2013-04-03 06:37:25 +00:00
Alan Cox
3fc10b7363 Introduce vm_radix_isleaf() and use it in a couple places. As compared to
using vm_radix_node_page() == NULL, the compiler is able to generate one
less conditional branch when vm_radix_isleaf() is used.  More use cases
involving the inner loops of vm_radix_insert(), vm_radix_lookup{,_ge,_le}(),
and vm_radix_remove() will follow.

Reviewed by:	attilio
Sponsored by:	EMC / Isilon Storage Division
2013-03-26 17:30:40 +00:00
Alan Cox
652615dcb7 Micro-optimize the control flow in a few places. Eliminate a panic call
that could never be reached in vm_radix_insert().  (If the pointer being
checked by the panic call were ever NULL, the immmediately preceding loop
would have already crashed on a NULL pointer dereference.)

Reviewed by:	attilio (an earlier version)
Sponsored by:	EMC / Isilon Storage Division
2013-03-24 16:43:07 +00:00
Attilio Rao
774d251d99 Sync back vmcontention branch into HEAD:
Replace the per-object resident and cached pages splay tree with a
path-compressed multi-digit radix trie.
Along with this, switch also the x86-specific handling of idle page
tables to using the radix trie.

This change is supposed to do the following:
- Allowing the acquisition of read locking for lookup operations of the
  resident/cached pages collections as the per-vm_page_t splay iterators
  are now removed.
- Increase the scalability of the operations on the page collections.

The radix trie does rely on the consumers locking to ensure atomicity of
its operations.  In order to avoid deadlocks the bisection nodes are
pre-allocated in the UMA zone.  This can be done safely because the
algorithm needs at maximum one new node per insert which means the
maximum number of the desired nodes is the number of available physical
frames themselves.  However, not all the times a new bisection node is
really needed.

The radix trie implements path-compression because UFS indirect blocks
can lead to several objects with a very sparse trie, increasing the number
of levels to usually scan.  It also helps in the nodes pre-fetching by
introducing the single node per-insert property.

This code is not generalized (yet) because of the possible loss of
performance by having much of the sizes in play configurable.
However, efforts to make this code more general and then reusable in
further different consumers might be really done.

The only KPI change is the removal of the function vm_page_splay() which
is now reaped.
The only KBI change, instead, is the removal of the left/right iterators
from struct vm_page, which are now reaped.

Further technical notes broken into mealpieces can be retrieved from the
svn branch:
http://svn.freebsd.org/base/user/attilio/vmcontention/

Sponsored by:	EMC / Isilon storage division
In collaboration with:	alc, jeff
Tested by:	flo, pho, jhb, davide
Tested by:	ian (arm)
Tested by:	andreast (powerpc)
2013-03-18 00:25:02 +00:00