define two new environment variables to better understand how much
memory is being allocated, and when. This has been invaluable in
inproving the --fit algorithm, and is likely to be useful when debugging
other memory-related issues.
`-lv 4` will be required to enable the following:
GGML_SYCL_MEMTRACE=1 will show per-site memory usage, updated whenever
it increases by more than 64MiB.
GGML_SYCL_MEMTRACE=2 will show every allocation and deallocation.
To change the default 64MiB threshold for reporting memory usage increases, use
GGML_SYCL_MEMTRACE_STEP.
A sample log line:
[SYCL-MEMTRACE] device memory query (dev): total 59493 MiB, free 4494, in use 54998; allocated 0 (buffers 0 + scratch 0), peak 0 MiB
improve the --fit algorithm to take into account the actual peak
required VRAM for a given context size on a SYCL backend.
This includes both properly accounting for how much VRAM is required
when the allocated context is fully used (which makes the reported
context drop below what it did before, but stop it OOMing) as well
as preventing some overly-conservative calculations which meant too much
VRAM was being reserved.
Tested on a Arc b70 with unsloth's qwen3.8 (Q4_K_XL), able to get 262144 context,
fully usable, with q8_0 KV and MTP and 4k ubatch size using --fit-target 1
