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dawn_wire: Directly use the data in deserialized buffer when possible

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This patch tries to use the data directly in deserialized buffer
when the data is "data-only" and doesn't affect the control flow instead
of allocating and copying into a temporary buffer. Due to the protection
of TOCTOU attacks, currently we only set "wire_is_data_only" on the
parameter "data" in Queue.WriteBuffer() and Queue.WriteTexture().

With this patch, the performance of dawn_perf_tests
BufferUploadPerf.Run/*_WriteBuffer_BufferSize_* with "-w" will
be greatly improved (~20%) when the upload buffer size is greater than
1MB.

BUG=chromium:1266727

Change-Id: I7a9d54c9b505975235ee37aa72ee97f082ad3aa3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/72063
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
This commit is contained in:
Jiawei Shao
2021-12-10 02:05:28 +00:00
committed by Dawn LUCI CQ
parent 6ad6278bc5
commit 1f25ea94bb
3 changed files with 34 additions and 20 deletions
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docs/codegen.md
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@@ -42,6 +42,7 @@ A **record** is a list of **record members**, each of which is a dictionary with
- `"length"` (default to 1 if not set), a string. Defines length of the array pointed to for pointer arguments. If not set the length is implicitly 1 (so not an array), but otherwise it can be set to the name of another member in the same record that will contain the length of the array (this is heavily used in the `fooCount` `foos` pattern in the API). As a special case `"strlen"` can be used for `const char*` record members to denote that the length should be determined with `strlen`.
- `"optional"` (default to false) a boolean that says whether this member is optional. Member records can be optional if they are pointers (otherwise dawn_wire will always try to dereference them), objects (otherwise dawn_wire will always try to encode their ID and crash), or if they have a `"default"` key. Optional pointers and objects will always default to `nullptr`.
- `"default"` (optional) a number or string. If set the record member will use that value as default value. Depending on the member's category it can be a number, a string containing a number, or the name of an enum/bitmask value.
- `"wire_is_data_only"` (default to false) a boolean that says whether it is safe to directly return a pointer of this member that is pointing to a piece of memory in the transfer buffer into dawn_wire. To prevent TOCTOU attacks, by default in dawn_wire we must ensure every single value returned to dawn_native a copy of what's in the wire, so `"wire_is_data_only"` is set to true only when the member is data-only and don't impact control flow.
**`"native"`**, doesn't have any other key. This is used to define native types that can be referenced by name in other things.