vm_radix trie.
Existing vm_radix_init() function is renamed to vm_radix_zinit().
Inlines moved out of the _ headers.
Reviewed by: alc, markj (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D11661
contain a vm_page_t at the specified index. However, with this
change, vm_radix_remove() no longer panics. Instead, it returns NULL
if there is no vm_page_t at the specified index. Otherwise, it
returns the vm_page_t. The motivation for this change is that it
simplifies the use of radix tries in the amd64, arm64, and i386 pmap
implementations. Instead of performing a lookup before every remove,
the pmap can simply perform the remove.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D8708
called to allocate a new page of radix trie nodes, there could be a call to
vm_radix_remove() on the same trie (of PG_CACHED pages) as the in-progress
vm_radix_insert(). With the removal of PG_CACHED pages, we can simplify
vm_radix_insert() and vm_radix_remove() by removing the flags on the root of
the trie that were used to detect this case and the code for restarting
vm_radix_insert() when it happened.
Reviewed by: kib, markj
Tested by: pho
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8664
These changes prevent sysctl(8) from returning proper output,
such as:
1) no output from sysctl(8)
2) erroneously returning ENOMEM with tools like truss(1)
or uname(1)
truss: can not get etype: Cannot allocate memory
there is an environment variable which shall initialize the SYSCTL
during early boot. This works for all SYSCTL types both statically and
dynamically created ones, except for the SYSCTL NODE type and SYSCTLs
which belong to VNETs. A new flag, CTLFLAG_NOFETCH, has been added to
be used in the case a tunable sysctl has a custom initialisation
function allowing the sysctl to still be marked as a tunable. The
kernel SYSCTL API is mostly the same, with a few exceptions for some
special operations like iterating childrens of a static/extern SYSCTL
node. This operation should probably be made into a factored out
common macro, hence some device drivers use this. The reason for
changing the SYSCTL API was the need for a SYSCTL parent OID pointer
and not only the SYSCTL parent OID list pointer in order to quickly
generate the sysctl path. The motivation behind this patch is to avoid
parameter loading cludges inside the OFED driver subsystem. Instead of
adding special code to the OFED driver subsystem to post-load tunables
into dynamically created sysctls, we generalize this in the kernel.
Other changes:
- Corrected a possibly incorrect sysctl name from "hw.cbb.intr_mask"
to "hw.pcic.intr_mask".
- Removed redundant TUNABLE statements throughout the kernel.
- Some minor code rewrites in connection to removing not needed
TUNABLE statements.
- Added a missing SYSCTL_DECL().
- Wrapped two very long lines.
- Avoid malloc()/free() inside sysctl string handling, in case it is
called to initialize a sysctl from a tunable, hence malloc()/free() is
not ready when sysctls from the sysctl dataset are registered.
- Bumped FreeBSD version to indicate SYSCTL API change.
MFC after: 2 weeks
Sponsored by: Mellanox Technologies
To reduce the diff struct pcu.cnt field was not renamed, so
PCPU_OP(cnt.field) is still used. pc_cnt and pcpu are also used in
kvm(3) and vmstat(8). The goal was to not affect externally used KPI.
Bump __FreeBSD_version_ in case some out-of-tree module/code relies on the
the global cnt variable.
Exp-run revealed no ports using it directly.
No objection from: arch@
Sponsored by: EMC / Isilon Storage Division
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
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
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
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
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
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
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
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
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
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
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)
