- VM_ALLOC_NOCREAT will grab without creating a page.
- vm_page_grab_valid() will grab and page in if necessary.
- vm_page_busy_acquire() automates some busy acquire loops.
Discussed with: alc, kib, markj
Tested by: pho (part of larger branch)
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21546
races with page busy state. The object lock is still used as an interlock
to ensure that the identity stays valid. Most callers should use
vm_page_sleep_if_busy() to handle the locking particulars.
Reviewed by: alc, kib, markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21255
There are several mechanisms by which a vm_page reference is held,
preventing the page from being freed back to the page allocator. In
particular, holding the page's object lock is sufficient to prevent the
page from being freed; holding the busy lock or a wiring is sufficent as
well. These references are protected by the page lock, which must
therefore be acquired for many per-page operations. This results in
false sharing since the page locks are external to the vm_page
structures themselves and each lock protects multiple structures.
Transition to using an atomically updated per-page reference counter.
The object's reference is counted using a flag bit in the counter. A
second flag bit is used to atomically block new references via
pmap_extract_and_hold() while removing managed mappings of a page.
Thus, the reference count of a page is guaranteed not to increase if the
page is unbusied, unmapped, and the object's write lock is held. As
a consequence of this, the page lock no longer protects a page's
identity; operations which move pages between objects are now
synchronized solely by the objects' locks.
The vm_page_wire() and vm_page_unwire() KPIs are changed. The former
requires that either the object lock or the busy lock is held. The
latter no longer has a return value and may free the page if it releases
the last reference to that page. vm_page_unwire_noq() behaves the same
as before; the caller is responsible for checking its return value and
freeing or enqueuing the page as appropriate. vm_page_wire_mapped() is
introduced for use in pmap_extract_and_hold(). It fails if the page is
concurrently being unmapped, typically triggering a fallback to the
fault handler. vm_page_wire() no longer requires the page lock and
vm_page_unwire() now internally acquires the page lock when releasing
the last wiring of a page (since the page lock still protects a page's
queue state). In particular, synchronization details are no longer
leaked into the caller.
The change excises the page lock from several frequently executed code
paths. In particular, vm_object_terminate() no longer bounces between
page locks as it releases an object's pages, and direct I/O and
sendfile(SF_NOCACHE) completions no longer require the page lock. In
these latter cases we now get linear scalability in the common scenario
where different threads are operating on different files.
__FreeBSD_version is bumped. The DRM ports have been updated to
accomodate the KPI changes.
Reviewed by: jeff (earlier version)
Tested by: gallatin (earlier version), pho
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D20486
Otherwise, we might left the boolean set, which would affect cleanup
after an error on interpreter activation.
Reviewed by: markj
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D21560
These were fully neutered in r177676 (2008), but not removed at the time for
unclear reasons. They're totally dead code, so go ahead and yank them now.
No functional change.
There are 2 problems:
- it introduces a funny bug where it can end up trylocking the same vnode [1]
- it exposes a pre-existing softdep deadlock [2]
Both are easier to run into that the bug which got fixed, so revert until
a complete solution is worked out.
Reported by: cy [1], pho [2]
Sponsored by: The FreeBSD Foundation
Currently the code only bumps holdcnt and clears the VI_FREE flag, not
performing actual vhold. Since the vnode is still visible elsewhere, a
potential new user can find it and incorrectly assume it is properly held.
Use vholdl instead to correctly hold the vnode. Another place recycling
(vlrureclaim) does this already.
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21522
r351650 switched posixshm to using OBJT_SWAP for shm_object
r351795 added support to the swap_pager for tracking writeable mappings
Take advantage of this and start tracking writeable mappings; fd sealing
will use this to reject a seal on writing with EBUSY if any such mapping
exist.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D21456
Currently writemapping accounting is only done for vnode_pager which does
some accounting on the underlying vnode.
Extend this to allow accounting to be possible for any of the pager types.
New pageops are added to update/release writecount that need to be
implemented for any pager wishing to do said accounting, and we implement
these methods now for both vnode_pager (unchanged) and swap_pager.
The primary motivation for this is to allow other systems with OBJT_SWAP
objects to check if their objects have any write mappings and reject
operations with EBUSY if so. posixshm will be the first to do so in order to
reject adding write seals to the shmfd if any writable mappings exist.
Reviewed by: kib, markj
Differential Revision: https://reviews.freebsd.org/D21456
It allows a process to request that stack gap was not applied to its
stacks, retroactively. Also it is possible to control the gaps in the
process after exec.
PR: 239894
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D21352
vnodes have 2 reference counts - holdcnt to keep the vnode itself from getting
freed and usecount to denote it is actively used.
Previously all operations bumping usecount would also bump holdcnt, which is
not necessary. We can detect if usecount is already > 1 (in which case holdcnt
is also > 1) and utilize it to avoid bumping holdcnt on our own. This saves
on atomic ops.
Reviewed by: kib
Tested by: pho (previous version)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21471
Previously userspace would issue one syscall to resolve the sysctl and then
another one to actually use it. Do it all in one trip.
Fallback is provided in case newer libc happens to be running on an older
kernel.
Submitted by: Pawel Biernacki
Reported by: kib, brooks
Differential Revision: https://reviews.freebsd.org/D17282
The initially read mount point can already be NULL.
Reported by: markj
Fixes: r351656 ("vfs: stop refing freed mount points in vop_stdgetwritemount")
Sponsored by: The FreeBSD Foundation
There is no correctness change here, but the procid lock is contended in
the fork path and taking it while holding proctree avoidably extends its
hold time.
Note that there are other ids which can end up getting cleared with the
lock.
Sponsored by: The FreeBSD Foundation
The page daemon periodically invokes uma_reclaim() to reclaim cached
items from each zone when the system is under memory pressure. This
is important since the size of these caches is unbounded by default.
However it also results in bursts of high latency when allocating from
heavily used zones as threads miss in the per-CPU caches and must
access the keg in order to allocate new items.
With r340405 we maintain an estimate of each zone's usage of its
(per-NUMA domain) cache of full buckets. Start making use of this
estimate to avoid reclaiming the entire cache when under memory
pressure. In particular, introduce TRIM, DRAIN and DRAIN_CPU
verbs for uma_reclaim() and uma_zone_reclaim(). When trimming, only
items in excess of the estimate are reclaimed. Draining a zone
reclaims all of the cached full buckets (the previous behaviour of
uma_reclaim()), and may further drain the per-CPU caches in extreme
cases.
Now, when under memory pressure, the page daemon will trim zones
rather than draining them. As a result, heavily used zones do not incur
bursts of bucket cache misses following reclamation, but large, unused
caches will be reclaimed as before.
Reviewed by: jeff
Tested by: pho (an earlier version)
MFC after: 2 months
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D16667
To permit larger values of MAXMEMDOM, which is currently 8 on amd64,
cpuset_setdomain(2) accepts a mask of size 256. In the kernel, domain
set masks are 64 bits wide, but can only represent a set of MAXMEMDOM
domains due to the use of the ds_order table.
Domain sets passed to cpuset_setdomain(2) are restricted to a subset
of their parent set, which is typically the root set, but before this
happens we modify the input set to exclude empty domains.
domainset_empty_vm() and other code which manipulates domain sets
expect the mask to be a subset of all_domains, so enforce that when
performing validation of cpuset_setdomain(2) parameters.
Reported and tested by: pho
Reviewed by: kib
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21477
The code used blindly ref based on an unsafely red address and then would
backpedal if necessary. This was safe in terms of memory access since
mounts are type-stable, but made for a potential a bug where the mount
was reused and had the count reset to 0 before this code decreased it.
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21411
Future changes to posixshm will start tracking writeable mappings in order
to support file sealing. Tracking writeable mappings for an OBJT_DEFAULT
object is complicated as it may be swapped out and converted to an
OBJT_SWAP. One may generically add this tracking for vm_object, but this is
difficult to do without increasing memory footprint of vm_object and blowing
up memory usage by a significant amount.
On the other hand, the swap pager can be expanded to track writeable
mappings without increasing vm_object size. This change is currently in
D21456. Switch over to OBJT_SWAP in advance of the other changes to the
swap pager and posixshm.
Current implementation of vnode_create_vobject() and
vnode_destroy_vobject() is written so that it prepared to handle the
vm object destruction for live vnode. Practically, no filesystems use
this, except for some remnants that were present in UFS till today.
One of the consequences of that model is that each filesystem must
call vnode_destroy_vobject() in VOP_RECLAIM() or earlier, as result
all of them get rid of the v_object in reclaim.
Move the call to vnode_destroy_vobject() to vgonel() before
VOP_RECLAIM(). This makes v_object stable: either the object is NULL,
or it is valid vm object till the vnode reclamation. Remove code from
vnode_create_vobject() to handle races with the parallel destruction.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D21412
vnode usecount drops to 0 all the time (e.g. for directories during path lookup).
When that happens the kernel would always lock the exclusive lock for the vnode
in order to call vinactive(). This blocks other threads who want to use the vnode
for looukp.
vinactive is very rarely needed and can be tested for without the vnode lock held.
This patch gives filesytems an opportunity to do it, sample total wait time for
tmpfs over 500 minutes of poudriere -j 104:
before: 557563641706 (lockmgr:tmpfs)
after: 46309603301 (lockmgr:tmpfs)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21371
It is not needed by anything in the kernel and it slightly drives up contention
on both proctree and allproc locks.
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21447
uiomove_object_page() and exec_map_first_page() would previously wire a
page after having grabbed it. Ask vm_page_grab() to perform the wiring
instead: this removes some redundant code, and is cheaper in the case
where the requested page is not resident since the page allocator can be
asked to initialize the page as wired, whereas a separate vm_page_wire()
call requires the page lock.
In vm_imgact_hold_page(), use vm_page_unwire_noq() instead of
vm_page_unwire(PQ_NONE). The latter ensures that the page is dequeued
before returning, but this is unnecessary since vm_page_free() will
trigger a batched dequeue of the page.
Reviewed by: alc, kib
Tested by: pho (part of a larger patch)
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21440
This field was not initialized in the !KERN_TLS case triggering an
assertion failure when using sendfile(2).
Reported by: pho, asomers
Sponsored by: Netflix
The plan is to drop the flags argument. There is also a temporary bug
now that nullfs ignores the flag.
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21252
- Don't add 1 to the result of DOMAINSET_FLS.
- Do not modify domainsets containing only empty domains.
- Always flatten a _PREFER policy to _ROUNDROBIN if the preferred
domain is empty. Previously we were doing this only when ds_cnt > 1.
These bugs could cause hangs during boot if a VM domain is empty.
Tested by: hselasky
Reviewed by: hselasky, kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21420
The function' interface assumes that the lower vnode is passed and
returned locked always.
Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
KTLS adds support for in-kernel framing and encryption of Transport
Layer Security (1.0-1.2) data on TCP sockets. KTLS only supports
offload of TLS for transmitted data. Key negotation must still be
performed in userland. Once completed, transmit session keys for a
connection are provided to the kernel via a new TCP_TXTLS_ENABLE
socket option. All subsequent data transmitted on the socket is
placed into TLS frames and encrypted using the supplied keys.
Any data written to a KTLS-enabled socket via write(2), aio_write(2),
or sendfile(2) is assumed to be application data and is encoded in TLS
frames with an application data type. Individual records can be sent
with a custom type (e.g. handshake messages) via sendmsg(2) with a new
control message (TLS_SET_RECORD_TYPE) specifying the record type.
At present, rekeying is not supported though the in-kernel framework
should support rekeying.
KTLS makes use of the recently added unmapped mbufs to store TLS
frames in the socket buffer. Each TLS frame is described by a single
ext_pgs mbuf. The ext_pgs structure contains the header of the TLS
record (and trailer for encrypted records) as well as references to
the associated TLS session.
KTLS supports two primary methods of encrypting TLS frames: software
TLS and ifnet TLS.
Software TLS marks mbufs holding socket data as not ready via
M_NOTREADY similar to sendfile(2) when TLS framing information is
added to an unmapped mbuf in ktls_frame(). ktls_enqueue() is then
called to schedule TLS frames for encryption. In the case of
sendfile_iodone() calls ktls_enqueue() instead of pru_ready() leaving
the mbufs marked M_NOTREADY until encryption is completed. For other
writes (vn_sendfile when pages are available, write(2), etc.), the
PRUS_NOTREADY is set when invoking pru_send() along with invoking
ktls_enqueue().
A pool of worker threads (the "KTLS" kernel process) encrypts TLS
frames queued via ktls_enqueue(). Each TLS frame is temporarily
mapped using the direct map and passed to a software encryption
backend to perform the actual encryption.
(Note: The use of PHYS_TO_DMAP could be replaced with sf_bufs if
someone wished to make this work on architectures without a direct
map.)
KTLS supports pluggable software encryption backends. Internally,
Netflix uses proprietary pure-software backends. This commit includes
a simple backend in a new ktls_ocf.ko module that uses the kernel's
OpenCrypto framework to provide AES-GCM encryption of TLS frames. As
a result, software TLS is now a bit of a misnomer as it can make use
of hardware crypto accelerators.
Once software encryption has finished, the TLS frame mbufs are marked
ready via pru_ready(). At this point, the encrypted data appears as
regular payload to the TCP stack stored in unmapped mbufs.
ifnet TLS permits a NIC to offload the TLS encryption and TCP
segmentation. In this mode, a new send tag type (IF_SND_TAG_TYPE_TLS)
is allocated on the interface a socket is routed over and associated
with a TLS session. TLS records for a TLS session using ifnet TLS are
not marked M_NOTREADY but are passed down the stack unencrypted. The
ip_output_send() and ip6_output_send() helper functions that apply
send tags to outbound IP packets verify that the send tag of the TLS
record matches the outbound interface. If so, the packet is tagged
with the TLS send tag and sent to the interface. The NIC device
driver must recognize packets with the TLS send tag and schedule them
for TLS encryption and TCP segmentation. If the the outbound
interface does not match the interface in the TLS send tag, the packet
is dropped. In addition, a task is scheduled to refresh the TLS send
tag for the TLS session. If a new TLS send tag cannot be allocated,
the connection is dropped. If a new TLS send tag is allocated,
however, subsequent packets will be tagged with the correct TLS send
tag. (This latter case has been tested by configuring both ports of a
Chelsio T6 in a lagg and failing over from one port to another. As
the connections migrated to the new port, new TLS send tags were
allocated for the new port and connections resumed without being
dropped.)
ifnet TLS can be enabled and disabled on supported network interfaces
via new '[-]txtls[46]' options to ifconfig(8). ifnet TLS is supported
across both vlan devices and lagg interfaces using failover, lacp with
flowid enabled, or lacp with flowid enabled.
Applications may request the current KTLS mode of a connection via a
new TCP_TXTLS_MODE socket option. They can also use this socket
option to toggle between software and ifnet TLS modes.
In addition, a testing tool is available in tools/tools/switch_tls.
This is modeled on tcpdrop and uses similar syntax. However, instead
of dropping connections, -s is used to force KTLS connections to
switch to software TLS and -i is used to switch to ifnet TLS.
Various sysctls and counters are available under the kern.ipc.tls
sysctl node. The kern.ipc.tls.enable node must be set to true to
enable KTLS (it is off by default). The use of unmapped mbufs must
also be enabled via kern.ipc.mb_use_ext_pgs to enable KTLS.
KTLS is enabled via the KERN_TLS kernel option.
This patch is the culmination of years of work by several folks
including Scott Long and Randall Stewart for the original design and
implementation; Drew Gallatin for several optimizations including the
use of ext_pgs mbufs, the M_NOTREADY mechanism for TLS records
awaiting software encryption, and pluggable software crypto backends;
and John Baldwin for modifications to support hardware TLS offload.
Reviewed by: gallatin, hselasky, rrs
Obtained from: Netflix
Sponsored by: Netflix, Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D21277
After all the changes, its dynamic scope is same as for MNTK_UNMOUNT,
but to allow the syncer vnode to be re-installed on unmount failure.
But the case of syncer was already handled by using the VV_FORCEINSMQ
flag for quite some time.
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
The Linux lockdep API assumes LA_LOCKED semantic in lockdep_assert_held(),
meaning that either a shared lock or write lock is Ok. On the other hand,
the timeout code uses lc_assert() with LA_XLOCKED, and we need both to
work.
For mutexes, because they can not be shared (this is unique among all lock
classes, and it is unlikely that we would add new lock class anytime soon),
it is easier to simply extend mtx_assert to handle LA_LOCKED there, despite
the change itself can be viewed as a slight abstraction violation.
Reviewed by: mjg, cem, jhb
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D21362
Without this patch, when an application performed lseek(SEEK_DATA/SEEK_HOLE)
on a file in a file system that does not have its own VOP_IOCTL(), the
lseek(2) fails with errno ENOTTY. This didn't seem appropriate, since
ENOTTY is not listed as an error return by either the lseek(2) man page
nor the POSIX draft for lseek(2).
This was discussed on freebsd-current@ here:
http://docs.FreeBSD.org/cgi/mid.cgi?CAOtMX2iiQdv1+15e1N_r7V6aCx_VqAJCTP1AW+qs3Yg7sPg9wA
This trivial patch maps ENOTTY to EINVAL for lseek(SEEK_DATA/SEEK_HOLE).
Reviewed by: markj
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D21300
They follow the conventions set by rw and sx lock probes. There is
an additional lockstat:::lockmgr-disown probe.
Update lockstat(1) to report on contention and hold events for
lockmgr locks. Document the new probes in dtrace_lockstat.4, and
deduplicate some of the existing probe descriptions.
Reviewed by: mjg
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21355
The original code came from a desire to minimize the number of updates
to v_wire_count, which prior to r329187 was updated using atomics.
However, there is no significant benefit to batching today, so simply
allocate pages using VM_ALLOC_WIRED and rely on system accounting.
Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D21323
