The pager getpages interface allows the caller to bound the number of
readahead and readbehind pages, and vm_fault_hold() makes use of this
feature. These bounds were ignored after r305056, causing the swap pager
to potentially page in more than the specified number of pages.
Reported and reviewed by: alc
X-MFC with: r305056
The swap_pager_swapoff() function uses trylock for the object lock
before pagein, which means that either i/o to md(4) over swap, or
intensive page faults over swap pager objects might prevent swapoff()
from making any progress. Then the retry < 100 check fails and machine
panics.
If trylock fails, acquire the object lock in the blockable way and
restart the hash bucket walk. Keep retries logic for now.
Reported and tested by: pho
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D7688
The removal of vm_fault_additional_pages() meant that a hard fault on
a swap-backed page would result in only that page being read in. This
change implements readahead and readbehind for the swap pager in
swap_pager_getpages(). swap_pager_haspage() is modified to return the
largest contiguous non-resident range of pages containing the requested
range.
Reviewed by: alc, kib
Tested by: pho
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7677
In particular, swapongeom_ev() needed event thread context when swap
pager configuration was performed under Giant and geom asserted that
Giant is not owned. Now both of the reason went away.
On the other hand, note that swpageom_release() is called from the
bio_done context, and possible close cannot be performed inline.
Also fix some minor issues. The swapgeom() function does not use the
td argument, remove it. Recheck that the vnode passed is still VCHR
and not reclaimed after the lock.
Reviewed by: mav
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Right now, all modifications of the list are locked by sw_alloc_mtx.
But initial lookup of the object by the handle in swap_pager_alloc()
is not protected by sw_alloc_mtx, which means that
vm_pager_object_lookup() could follow freed pointer.
Create a new named swap object with the OBJT_SWAP type, instead
of OBJT_DEFAULT. With this change, swp_pager_meta_build() never need
to upgrade named OBJT_DEFAULT to OBJT_SWAP (in the other place, we do
not forbid for client code to create named OBJT_DEFAULT objects at
all).
That change allows to remove sw_alloc_mtx and make the list locked by
sw_alloc_sx lock. Update swap_pager_copy() to new locking mode.
Create helper swap_pager_alloc_init() to consolidate named and
anonymous swap objects creation, while a caller ensures that the
neccesary locks are held around the helper.
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Approved by: re (hrs)
Existing issue of not protecting pager_object_list iteration in
vm_pager_object_lookup() by sw_alloc_mtx is not affected by Giant
removal.
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
o With new KPI consumers can request contiguous ranges of pages, and
unlike before, all pages will be kept busied on return, like it was
done before with the 'reqpage' only. Now the reqpage goes away. With
new interface it is easier to implement code protected from race
conditions.
Such arrayed requests for now should be preceeded by a call to
vm_pager_haspage() to make sure that request is possible. This
could be improved later, making vm_pager_haspage() obsolete.
Strenghtening the promises on the business of the array of pages
allows us to remove such hacks as swp_pager_free_nrpage() and
vm_pager_free_nonreq().
o New KPI accepts two integer pointers that may optionally point at
values for read ahead and read behind, that a pager may do, if it
can. These pages are completely owned by pager, and not controlled
by the caller.
This shifts the UFS-specific readahead logic from vm_fault.c, which
should be file system agnostic, into vnode_pager.c. It also removes
one VOP_BMAP() request per hard fault.
Discussed with: kib, alc, jeff, scottl
Sponsored by: Nginx, Inc.
Sponsored by: Netflix
locking and doesn't sleep. Flag the consumer we create as such. In
addition, decrement the in flight index when we have an out of memory
error after having incremented it previously. This would have
prevented swapoff from working if the swap pager ever hit a resource
shortage trying to swap out something (the swap in path always waits
for a bio, so won't have this issue). Simplify the close logic by
abandoning the use of private and initializing the index to 1 and
dropping that reference when we previously set private.
Also, set sw_id only while sw_dev_mtx is held. This should only affect
swapping to a vnode, as opposed to a geom whose close always sets it to
NULL with sw_dev_mtx held.
Differential Review: https://reviews.freebsd.org/D3547
- Use pointer assignment rather than a combination of pointers and
flags to switch buffers between unmapped and mapped. This eliminates
multiple flags and generally simplifies the logic.
- Eliminate b_saveaddr since it is only used with pager bufs which have
their b_data re-initialized on each allocation.
- Gather up some convenience routines in the buffer cache for
manipulating buf space and buf malloc space.
- Add an inline, buf_mapped(), to standardize checks around unmapped
buffers.
In collaboration with: mlaier
Reviewed by: kib
Tested by: pho (many small revisions ago)
Sponsored by: EMC / Isilon Storage Division
o Provide an extensive set of assertions for input array of pages.
o Remove now duplicate assertions from different pagers.
Sponsored by: Nginx, Inc.
Sponsored by: Netflix
Use the same scheme implemented to manage credentials.
Code needing to look at process's credentials (as opposed to thred's) is
provided with *_proc variants of relevant functions.
Places which possibly had to take the proc lock anyway still use the proc
pointer to access limits.
This is ok since objects come from a NOFREE zone and allows objects to
be locked while traversing the object list without triggering a LOR.
Ensure that objects on the list are marked DEAD while free or stillborn,
and that they have a refcount of zero. This required updating most of
the pagers to explicitly mark an object as dead when deallocating it.
(Only the vnode pager did this previously.)
Differential Revision: https://reviews.freebsd.org/D2423
Reviewed by: alc, kib (earlier version)
MFC after: 2 weeks
Sponsored by: Norse Corp, Inc.
in the main swapper work cycle, do it in the sysctl handler. This removes
extra mutex acquisition from the main cycle and makes the sysctl knob return
error on an invalid value, instead of accepting and fixing it.
Reviewed by: kib
Sponsored by: Netflix
Sponsored by: Nginx, Inc.
The point of this is to be able to add RACCT (with RACCT_DISABLED)
to GENERIC, to avoid having to rebuild the kernel to use rctl(8).
Differential Revision: https://reviews.freebsd.org/D2369
Reviewed by: kib@
MFC after: 1 month
Relnotes: yes
Sponsored by: The FreeBSD Foundation
Swap device is still reported as enabled, and system still may crash later
if some swapped-out kernel pages were lost with the device, but at least
GEOM and CAM can now release the lost disk, allowing it to be reconnected.
MFC after: 2 weeks
Sponsored by: iXsystems, Inc.
o Provide a new VOP_GETPAGES_ASYNC(), which works like VOP_GETPAGES(), but
doesn't sleep. It returns immediately, and will execute the I/O done handler
function that must be supplied as argument.
o Provide VOP_GETPAGES_ASYNC() for the FFS, which uses vnode_pager.
o Extend pagertab to support pgo_getpages_async method, and implement this
method for vnode_pager.
Reviewed by: kib
Tested by: pho
Sponsored by: Netflix
Sponsored by: Nginx, Inc.
default_pager_putpages() and swap_pager_putpages().
It is the same fix as was done for vnode_pager_putpages()
in r271586.
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
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
then threads can sleep on the pip condition.
Avoid to deadlock such threads by correctly awakening the sleeping ones
after the pip is finished.
swapoff side of the bug can likely result in shutdown deadlocks.
Sponsored by: EMC / Isilon Storage Division
Reported by: pho, pluknet
Tested by: pho
The flag was mandatory since r209792, where vm_page_grab(9) was
changed to only support the alloc retry semantic.
Suggested and reviewed by: alc
Sponsored by: The FreeBSD Foundation
Unify the 2 concept into a real, minimal, sxlock where the shared
acquisition represent the soft busy and the exclusive acquisition
represent the hard busy.
The old VPO_WANTED mechanism becames the hard-path for this new lock
and it becomes per-page rather than per-object.
The vm_object lock becames an interlock for this functionality:
it can be held in both read or write mode.
However, if the vm_object lock is held in read mode while acquiring
or releasing the busy state, the thread owner cannot make any
assumption on the busy state unless it is also busying it.
Also:
- Add a new flag to directly shared busy pages while vm_page_alloc
and vm_page_grab are being executed. This will be very helpful
once these functions happen under a read object lock.
- Move the swapping sleep into its own per-object flag
The KPI is heavilly changed this is why the version is bumped.
It is very likely that some VM ports users will need to change
their own code.
Sponsored by: EMC / Isilon storage division
Discussed with: alc
Reviewed by: jeff, kib
Tested by: gavin, bapt (older version)
Tested by: pho, scottl
to drain the reserve. This was broken in r243040, causing deadlock.
Note that VM_WAIT call in case of uma_zalloc() failure from pagedaemon
would only wait for the v_pageout_free_min anyway.
Reported and tested by: pho
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
Avoid to busy/unbusy a page in cases where there is no need to drop the
vm_obj lock, more nominally when the page is full valid after
vm_page_grab().
Sponsored by: EMC / Isilon storage division
Reviewed by: alc
It can now be accessed with a write lock on the object containing it OR
with a read lock on the object containing it along with the swhash_mtx.
o Remove some duplicate assertions for swap_pager_freespace() and
swap_pager_unswapped() but keep the object locking references for
documentation.
Sponsored by: EMC / Isilon storage division
Reviewed by: alc
* VM_OBJECT_LOCK and VM_OBJECT_UNLOCK are mapped to write operations
* VM_OBJECT_SLEEP() is introduced as a general purpose primitve to
get a sleep operation using a VM_OBJECT_LOCK() as protection
* The approach must bear with vm_pager.h namespace pollution so many
files require including directly rwlock.h
tick until the situation is resolved (if ever), just print a single
message when running out and another when space becomes available.
- When adding more swap, warn if the total amount exceeds half the
theoretical maximum we can handle.
layer, but it is read directly by the MI VM layer. This change introduces
pmap_page_is_write_mapped() in order to completely encapsulate all direct
access to PGA_WRITEABLE in the pmap layer.
Aesthetics aside, I am making this change because amd64 will likely begin
using an alternative method to track write mappings, and having
pmap_page_is_write_mapped() in place allows me to make such a change
without further modification to the MI VM layer.
As an added bonus, tidy up some nearby comments concerning page flags.
Reviewed by: kib
MFC after: 6 weeks
