Buffer and DeviceBuffer created their VkBuffer at the pool's size class, so
a robust read past the requested size stayed in bounds and returned the
bytes an earlier user of the pooled memory left there instead of an
out-of-range result. Each VkBuffer now has the requested size, created with
the pool's usage, over memory of its class (or its slab slot); one taken
from the pool for a different size is recreated over the same memory at
the same offset. agc_buffer_pool follows a pooled buffer by its memory, so
its class and reuse cases hold with the exact-size buffers.
Every small host buffer (size classes below 1 MiB: draw and dispatch data,
copied regions, snapshots) had a VkDeviceMemory of its own. When the pool
missed, the worker paid a vkAllocateMemory and vkMapMemory, and the release
thread a vkUnmapMemory and vkFreeMemory, for each one. The frees also stall
the worker's vkQueueSubmit in the driver.
A host-visible buffer of a size class now gets its own VkBuffer bound into a
slot of a shared block (2 MiB, or 8 slots for the large classes) per memory
type, size class and device-address use, mapped once. Releasing it destroys
only the VkBuffer and returns the slot; a block is freed when it empties and
its slab already keeps an empty one. A slot is used only when the buffer's
alignment and the non-coherent atom divide its size class, so the slot
offset is valid for the bind and Invalidate covers exactly the slot. The
pool still retains released buffers by class as before; only what backs
them changed.
The device-local tier of BufferPool only reused a buffer of the exact
size and usage it was asked for. Partial storage-image detiles and
retiles ask for a new size and the other transfer direction almost
every time, so the tier sat at its budget and missed and evicted
dozens of buffers per frame, and the vkFreeMemory calls on the release
thread held up submits and allocations on the recording threads.
Device-tier requests of 1 MiB and more now round up to an eighth of
their octave, the tier's buffers are created for storage and both
transfer directions, and a request takes the smallest retained buffer
from its own class up to twice its size. Host tiers, the budget and
eviction are unchanged. agc_buffer_pool covers the classes, the fit
and its bound, reuse only after release, the budget and the unchanged
lists.
Sanjaysrinivas
TideOPL
Dean Galvin
Celegans12