[#970] fstree: Add linux-specific file writer using O_TMPFILE
O_TMPFILE is implemented for all modern FSes and it's much easier and safer to
use. If application crashes in the middle of writing this file would be gone
and won't leave any garbage.
Notice that this implementation makes a different choice wrt EEXIST handling,
generic one always overwrites, while this one keeps the old data.
There is no real performance difference.
SSD (slow&old), XFS, Core i7-8565U:
Sync
```
name old time/op new time/op delta
Put/size=1024,thread=1/fstree-8 1.74ms ± 3% 0.06ms ± 7% -96.31% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 10.0ms ±41% 1.1ms ±18% -88.95% (p=0.000 n=9+10)
Put/size=1024,thread=100/fstree-8 32.3ms ±60% 6.5ms ±14% -79.97% (p=0.000 n=10+10)
Put/size=1048576,thread=1/fstree-8 17.8ms ±90% 3.4ms ±70% -81.08% (p=0.000 n=10+10)
Put/size=1048576,thread=20/fstree-8 103ms ±174% 112ms ±158% ~ (p=0.971 n=10+10)
Put/size=1048576,thread=100/fstree-8 949ms ±78% 583ms ±132% ~ (p=0.089 n=10+10)
name old alloc/op new alloc/op delta
Put/size=1024,thread=1/fstree-8 3.17kB ± 1% 1.96kB ± 0% -38.09% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 59.6kB ± 1% 39.2kB ± 1% -34.30% (p=0.000 n=8+10)
Put/size=1024,thread=100/fstree-8 299kB ± 0% 198kB ± 0% -33.90% (p=0.000 n=7+9)
Put/size=1048576,thread=1/fstree-8 3.38kB ± 1% 2.36kB ± 1% -30.22% (p=0.000 n=10+10)
Put/size=1048576,thread=20/fstree-8 65.7kB ± 4% 47.7kB ± 6% -27.27% (p=0.000 n=10+10)
Put/size=1048576,thread=100/fstree-8 351kB ± 8% 245kB ± 8% -30.22% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
Put/size=1024,thread=1/fstree-8 30.3 ± 2% 21.0 ± 0% -30.69% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 554 ± 1% 413 ± 0% -25.35% (p=0.000 n=8+10)
Put/size=1024,thread=100/fstree-8 2.77k ± 0% 2.07k ± 0% -25.27% (p=0.000 n=7+10)
Put/size=1048576,thread=1/fstree-8 32.0 ± 0% 25.0 ± 0% -21.88% (p=0.000 n=9+8)
Put/size=1048576,thread=20/fstree-8 609 ± 5% 494 ± 6% -18.93% (p=0.000 n=10+10)
Put/size=1048576,thread=100/fstree-8 3.25k ± 9% 2.50k ± 8% -23.21% (p=0.000 n=10+10)
```
No sync
```
name old time/op new time/op delta
Put/size=1024,thread=1/fstree-8 71.3µs ±10% 59.8µs ±10% -16.21% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 1.43ms ± 6% 1.22ms ±13% -14.53% (p=0.000 n=10+10)
Put/size=1024,thread=100/fstree-8 8.12ms ± 3% 6.36ms ± 2% -21.67% (p=0.000 n=8+9)
Put/size=1048576,thread=1/fstree-8 1.88ms ±70% 1.61ms ±78% ~ (p=0.393 n=10+10)
Put/size=1048576,thread=20/fstree-8 32.7ms ±28% 34.2ms ±112% ~ (p=0.968 n=9+10)
Put/size=1048576,thread=100/fstree-8 262ms ±56% 226ms ±34% ~ (p=0.447 n=10+9)
name old alloc/op new alloc/op delta
Put/size=1024,thread=1/fstree-8 2.89kB ± 0% 1.96kB ± 0% -32.28% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 58.2kB ± 0% 39.5kB ± 0% -32.09% (p=0.000 n=8+8)
Put/size=1024,thread=100/fstree-8 291kB ± 0% 198kB ± 0% -32.19% (p=0.000 n=9+9)
Put/size=1048576,thread=1/fstree-8 3.05kB ± 1% 2.13kB ± 1% -30.16% (p=0.000 n=10+9)
Put/size=1048576,thread=20/fstree-8 62.6kB ± 0% 44.3kB ± 0% -29.23% (p=0.000 n=9+9)
Put/size=1048576,thread=100/fstree-8 302kB ± 0% 210kB ± 1% -30.39% (p=0.000 n=9+9)
name old allocs/op new allocs/op delta
Put/size=1024,thread=1/fstree-8 27.0 ± 0% 21.0 ± 0% -22.22% (p=0.000 n=10+10)
Put/size=1024,thread=20/fstree-8 539 ± 0% 415 ± 0% -22.98% (p=0.000 n=10+10)
Put/size=1024,thread=100/fstree-8 2.69k ± 0% 2.07k ± 0% -23.09% (p=0.000 n=9+9)
Put/size=1048576,thread=1/fstree-8 28.0 ± 0% 22.3 ± 3% -20.36% (p=0.000 n=8+10)
Put/size=1048576,thread=20/fstree-8 577 ± 0% 458 ± 0% -20.72% (p=0.000 n=9+9)
Put/size=1048576,thread=100/fstree-8 2.76k ± 0% 2.15k ± 0% -22.05% (p=0.000 n=9+8)
```
HDD (LVM), ext4, Ryzen 5 1600:
Sync
```
│ fs.sync-generic │ fs.sync-linux │
│ sec/op │ sec/op vs base │
Put/size=1024,thread=1/fstree-12 34.70m ± 19% 33.59m ± 16% ~ (p=0.529 n=10)
Put/size=1024,thread=20/fstree-12 188.8m ± 8% 189.2m ± 16% ~ (p=0.739 n=10)
Put/size=1024,thread=100/fstree-12 264.8m ± 22% 273.6m ± 28% ~ (p=0.353 n=10)
Put/size=1048576,thread=1/fstree-12 54.90m ± 14% 47.08m ± 18% ~ (p=0.063 n=10)
Put/size=1048576,thread=20/fstree-12 244.1m ± 14% 220.4m ± 22% ~ (p=0.579 n=10)
Put/size=1048576,thread=100/fstree-12 847.2m ± 5% 893.6m ± 3% +5.48% (p=0.000 n=10)
geomean 164.3m 158.9m -3.29%
│ fs.sync-generic │ fs.sync-linux │
│ B/op │ B/op vs base │
Put/size=1024,thread=1/fstree-12 3.375Ki ± 1% 2.471Ki ± 1% -26.80% (p=0.000 n=10)
Put/size=1024,thread=20/fstree-12 66.62Ki ± 6% 49.21Ki ± 6% -26.15% (p=0.000 n=10)
Put/size=1024,thread=100/fstree-12 319.2Ki ± 1% 230.9Ki ± 2% -27.64% (p=0.000 n=10)
Put/size=1048576,thread=1/fstree-12 3.457Ki ± 1% 2.559Ki ± 1% -25.97% (p=0.000 n=10)
Put/size=1048576,thread=20/fstree-12 66.91Ki ± 1% 49.16Ki ± 1% -26.52% (p=0.000 n=10)
Put/size=1048576,thread=100/fstree-12 338.8Ki ± 2% 252.3Ki ± 3% -25.54% (p=0.000 n=10)
geomean 42.17Ki 31.02Ki -26.44%
│ fs.sync-generic │ fs.sync-linux │
│ allocs/op │ allocs/op vs base │
Put/size=1024,thread=1/fstree-12 33.00 ± 0% 27.00 ± 0% -18.18% (p=0.000 n=10)
Put/size=1024,thread=20/fstree-12 639.5 ± 1% 519.0 ± 2% -18.84% (p=0.000 n=10)
Put/size=1024,thread=100/fstree-12 3.059k ± 1% 2.478k ± 2% -18.99% (p=0.000 n=10)
Put/size=1048576,thread=1/fstree-12 33.50 ± 1% 28.00 ± 4% -16.42% (p=0.000 n=10)
Put/size=1048576,thread=20/fstree-12 638.5 ± 1% 520.0 ± 1% -18.56% (p=0.000 n=10)
Put/size=1048576,thread=100/fstree-12 3.209k ± 2% 2.655k ± 2% -17.28% (p=0.000 n=10)
geomean 405.3 332.1 -18.05%
```
No sync
```
│ fs.nosync-generic │ fs.nosync-linux │
│ sec/op │ sec/op vs base │
Put/size=1024,thread=1/fstree-12 148.2µ ± 20% 136.6µ ± 19% -7.89% (p=0.029 n=10)
Put/size=1024,thread=20/fstree-12 1.140m ± 26% 1.364m ± 16% ~ (p=0.143 n=10)
Put/size=1024,thread=100/fstree-12 11.93m ± 68% 26.89m ± 62% ~ (p=0.123 n=10)
Put/size=1048576,thread=1/fstree-12 1.302m ± 3% 1.287m ± 5% ~ (p=0.481 n=10)
Put/size=1048576,thread=20/fstree-12 77.52m ± 8% 74.07m ± 7% ~ (p=0.278 n=10+9)
Put/size=1048576,thread=100/fstree-12 226.1m ± ∞ ¹
geomean 5.986m 3.434m +18.60% ²
¹ need >= 6 samples for confidence interval at level 0.95
² benchmark set differs from baseline; geomeans may not be comparable
│ fs.nosync-generic │ fs.nosync-linux │
│ B/op │ B/op vs base │
Put/size=1024,thread=1/fstree-12 2.879Ki ± 0% 1.972Ki ± 0% -31.51% (p=0.000 n=10)
Put/size=1024,thread=20/fstree-12 55.94Ki ± 1% 37.90Ki ± 1% -32.25% (p=0.000 n=10)
Put/size=1024,thread=100/fstree-12 272.6Ki ± 0% 182.1Ki ± 9% -33.21% (p=0.000 n=10)
Put/size=1048576,thread=1/fstree-12 3.158Ki ± 0% 2.259Ki ± 0% -28.46% (p=0.000 n=10)
Put/size=1048576,thread=20/fstree-12 58.87Ki ± 0% 41.03Ki ± 0% -30.30% (p=0.000 n=10+9)
Put/size=1048576,thread=100/fstree-12 299.8Ki ± ∞ ¹
geomean 36.71Ki 16.60Ki -31.17% ²
¹ need >= 6 samples for confidence interval at level 0.95
² benchmark set differs from baseline; geomeans may not be comparable
│ fs.nosync-generic │ fs.nosync-linux │
│ allocs/op │ allocs/op vs base │
Put/size=1024,thread=1/fstree-12 28.00 ± 0% 22.00 ± 0% -21.43% (p=0.000 n=10)
Put/size=1024,thread=20/fstree-12 530.0 ± 0% 407.5 ± 1% -23.11% (p=0.000 n=10)
Put/size=1024,thread=100/fstree-12 2.567k ± 0% 1.956k ± 9% -23.77% (p=0.000 n=10)
Put/size=1048576,thread=1/fstree-12 30.00 ± 0% 24.00 ± 0% -20.00% (p=0.000 n=10)
Put/size=1048576,thread=20/fstree-12 553.5 ± 0% 434.0 ± 0% -21.59% (n=10+9)
Put/size=1048576,thread=100/fstree-12 2.803k ± ∞ ¹
geomean 347.9 178.8 -21.99% ²
¹ need >= 6 samples for confidence interval at level 0.95
² benchmark set differs from baseline; geomeans may not be comparable
```
Signed-off-by: Roman Khimov <roman@nspcc.ru>
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
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