Resolves#4943's draw relocation against this branch: tagVariantRuns, which now builds a draw variant's runs and words, also records the captured words it shares with a table's supplied blocks, per region as before. A variant whose runs relocation splits keeps sharing for the draw cache's word compare, and skips the vouched validation, which already requires one run per region.
The line said FormatVersion 36 while the code is at 37, as main's says 33 against 36. Without the number it no longer goes stale on each bump or conflicts between PRs that bump it.
The logger thread, the bounded queue that blocks its caller, the LogSink
hook, APS5_LOG_SYNC and APS5_LOG_STATS, where the queue is flushed and
what stays outside it: direct fprintf(stderr) and printf calls are written
at once, so they can appear before older queued lines.
Brings the series onto main 4e9a2a871 (#1193, #1201, #1202, #6060,
#6333 and the descriptor word tracking of 682b07eb0).
Resolutions:
- ShaderMemory: the column memo's supplied and spilled blocks now sit
on #1193's page vector, page pool and word masks. Pages are found by
binary search, since a spilled block can add many pages, and a block
placed into a lazily read page fills the rest of the 16-word blocks it
touches, so a later lazy read never overwrites placed words.
- ResourceMaterializer and SharedValues: the selected-record path and
the words index carry availableDwordMask, as the snapshot hash does.
A selected record's dwords past the end of its buffer count as read
zeros, which is what a scalar buffer load returns there, so a key past
the heap still selects a null image without reading the heap.
- DescriptorCache: kept table sets live beside #1201's recycled sets.
- Tests and CMake: both sides' tests are kept.
The draw cache sets each fresh stage capture against the variants it keeps (insertDrawEntry), and
the dispatch cache sets a fresh capture against its front variant, by comparing every captured word.
A 32,768-record table column is 262,144 of them, so each compare went through 1 MiB on each side
even when both captures had copied the column from the same shared block.
A variant now records the words it copied from a block the shader memory shares (SharedWords: where
they sit in the capture and in the block, and a weak reference to the block; consecutive pages of
one block join into one entry). SameCapturedWords takes the words both captures copied from the
same place of the same block as equal, since a block never changes, and compares the words around
them as before. Two blocks with equal words, words read into pages and a released block fall back
to the word compare. The reference is weak, so a kept variant holds no block alive, and a released
block's identity cannot pass to a new one: its control block stays until the last weak reference
goes.
A result memo miss resolves every image table of the snapshot again: ResolveImageTables decodes each
distinct T#, builds the element and poison indices and fills one map record per key, which is most
of a miss for a large table. A miss whose table did not change is common: another buffer, flat SRT
word or user data word changes the result key while the column is the one the column memo shares.
ResolveImageTablesShared keeps the last resolutions and hands one out by reference when the variant
(its id), the reducing state of the direct samplers paired with table images and every column match:
base, size, records, keys, fault, outside, and the column's codes and distinct T#s by identity. The
memo holds those shared values, so a block it compares cannot be freed and reused for other words;
a column read again is a new block and resolves again even when its words are equal.
It keeps at most 4 resolutions per variant and 256 in all within 8 Mi words, counting the columns
their keys keep alive, least recently used first out, under one mutex. A resolution is immutable
once made and is shared between threads read-only. APS5_NO_TABLE_RESOLUTION_REUSE=1 turns it off.
ImageTableReuseCounts gains the resolutions made and the ones shared.
When the write tracker vouched for an unwritten image table column, the capture still copied each of
its words into ShaderMemory's pages (supplyWords) so they would be in the captured regions, and
Regions() then found them again bit by bit. On a 32,768-record column that is a 1 MiB copy per
capture (about 120 us here) and a scan of 262,144 read bits per Regions() call (about 230 us), and
the draw path calls TakeRecentRegions() and Regions() once each per stage.
The memo now keeps a column's words in one immutable block (SrtGuestWords), and supplyWords hands
that block over. ShaderMemory keeps a reference and reports its runs page by page, the regions a
read of the same words reports, merged in address order with the pages and the initial regions; a
second stage that supplies the same block only marks it recent again. The words reach pages only
when they must: a later read in the same ShaderMemory that touches them first moves the whole block
into its pages (spilled), so a word is never reported twice, and a block that overlaps pages already
fetched or another block's runs is copied as before. A spilled block stays referenced until the
ShaderMemory goes, so the regions already taken from it stay valid. ShaderMemory::Supplies() counts
the words shared, copied and spilled.
A capture that reused a memoized image table column still copied it: each record's state and code
and the distinct T#s went from the memo into the snapshot, the snapshot rebuilt its codes from the
states, and the column's per-record vectors were allocated before the memo was even looked up. Every
Recompile then hashed the codes and the distinct T#s word by word for the result memo. On a
32,768-record column of distinct T#s that was about 155 us of copying per capture and 410 us of
hashing per Recompile here, for a column nothing wrote.
A column is now built once into immutable shared values (SharedValues: its codes, its distinct T#s
and its read ranges) and the memo keeps that column. A capture that reuses it takes a reference, so
two captures of an unchanged table share one column and copy nothing, and the per-record vectors
are allocated only when the column is walked. The codes index the column's own distinct T#s
(ImageTableColumnSnapshot::words) instead of a list shared by the shader's columns, so every column
of a shader is shared whole, not only the first. A column read again after a write is a new one:
the snapshots holding the old one keep it unchanged. The result memo hashes each shared value once
and keeps the hash in it; equal contents hash equal whether they are shared or not.
ImageTableReuseCounts gains the reuses that shared a column and the columns built.
Yunus Shaikh