If only 2 page frames are queued and code executing in one frame is
making an access to memory in the second frame then the access will trap
and k_mem_paging_eviction_accessed() will be called to move that frame
to the end of the queue ... marking the new head frame unaccessible.
But that newly unaccessible frame contains the code that has yet to be
resumed to perform its memory access. Since it is now unaccessible, a
trap is triggered, the frame is moved to the end of the queue and the
new head frame (the one we trapped for initially) is marked unaccessible.
Execution is resumed with the memory access which is unaccessible again
and the cycle repeats infinitely.
Fix this by not marking the new head unaccessible if there is only one
queued frame left in the queue.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
The first page frame index was reserved for head and tail ^pointers.
However there are cases where the first frame is actually made
evictable and would trigger the assertion guarding against that.
Fix this by applying an offset to actual frame indexes.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This is a O(1) LRU eviction algorithm. A bit more complex but way more
scalable than the NRU algorithm.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Let eviction algorithms be notified when a given page frame:
- should be considered as possible candidate
- should no longer be considered as candidate
- has just been marked as "accessed"
The NRU algorithm is unchanged so it implements those as empty stubs.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Currently, the NRU algorithm always picks the lowest (and very often the
same) clean unaccessed page over and over when e.g. doing large anonymous
memory mappings. Spread the eviction selection more uniformly by by
starting the search right after the last victim instead of always
restarting from 0.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Also any demand paging and page frame related bits are
renamed.
This is part of a series to move memory management related
stuff out of the Z_ namespace into its own namespace.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Introduce z_page_frame_set() and z_page_frame_clear() to manipulate
flags. Obtain the virtual address using the existing
z_page_frame_to_virt(). This will make changes to the page frame
structure easier.
Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This moves including of demand_paging.h out of kernel/mm.h,
so that users of demand paging APIs must include the header
explicitly. Since the main user is kernel itself, we can be
more discipline about header inclusion.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
irq_lock() returns an unsigned integer key.
Generated by spatch using semantic patch
scripts/coccinelle/irq_lock.cocci
Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>
In order to bring consistency in-tree, migrate all subsystems code to
the new prefix <zephyr/...>. Note that the conversion has been scripted,
refer to zephyrproject-rtos#45388 for more details.
Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
In k_mem_paging_eviction_select(), the returned dirty bit value
may not be actually associated with the page selected, but
rather the last page examined. So fix this.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
These functions and data structures are those that need
to be implemented by eviction algorithm and application
outside kernel. Promote them from z_* so these can be
included in documentation.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
Backing stores and eviction algorithms will be included here.
Exactly one must be chosen, with a default option to leave
the implementation to the application.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
Backing stores and eviction algorithms will be included here.
Exactly one must be chosen, with a default option to leave
the implementation to the application.
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
