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README.txt
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README.txt
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create an overlay-based directory tree with a large file in the lower dir
mkdir ./merged ./work ./upper ./lower
dd if=/dev/zero of=./lower/a bs=$((1 << 12)) count=$((1 << 18))
262144+0 records in
262144+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.804386 s, 1.3 GB/s
sudo mount \
-t overlay \
overlay \
-o lowerdir=./lower,upperdir=./upper,workdir=./work \
./merged
tree
.
├── lower
│ └── a
├── merged
│ └── a
└── upper
(this can be done with `make setup`)
run the tracer, and then perform a `chown(2)` in `merged/a` to see the cost of a
copy up
sudo ./trace.bt
PID COMM NAME LEN(B) ELAPSED (ms)
12752 a.out ./merged/a 1073741824 780
(for an example `chown(2)`ing thing, see `./main.c`)
LICENSE - MIT