Use the write amplification value calculated by RocksDB in benchmark.sh (#8915)

Summary:
Currently, `benchmark.sh` computes write amplification itself; the patch
changes the script to use the value calculated by RocksDB (which is
printed as part of the periodic statistics). This also has the benefit
of being correct for BlobDB as well, since it also considers the amount
of data written to blob files.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8915

Test Plan:
```
DB_DIR=/tmp/rocksdbtest/dbbench/ WAL_DIR=/tmp/rocksdbtest/dbbench/ NUM_KEYS=20000000 NUM_THREADS=32 tools/benchmark.sh overwrite --enable_blob_files=1 --enable_blob_garbage_collection=1

...

** Compaction Stats [default] **
Level    Files   Size     Score Read(GB)  Rn(GB) Rnp1(GB) Write(GB) Wnew(GB) Moved(GB) W-Amp Rd(MB/s) Wr(MB/s) Comp(sec) CompMergeCPU(sec) Comp(cnt) Avg(sec) KeyIn KeyDrop Rblob(GB) Wblob(GB)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  L0      7/5   43.93 MB   0.5      0.3     0.0      0.3       0.5      0.3       0.0   1.0      1.3     59.9    201.35            101.88       109    1.847     22M   499K       0.0      11.2
  L4      4/4   244.03 MB   0.0     11.4     0.3      1.6       1.6      0.0       0.0   1.1     50.6     49.3    231.10            288.84         7   33.014    156M    26M       9.5       9.5
  L5     36/0    3.28 GB   0.0      0.0     0.0      0.0       0.0      0.0       0.0   0.0      0.0      0.0      0.00              0.00         0    0.000       0      0       0.0       0.0
 Sum     47/9    3.56 GB   0.0     11.7     0.3      1.8       2.2      0.3       0.0   2.0     27.6     54.3    432.45            390.72       116    3.728    179M    26M       9.5      20.8
 Int      0/0    0.00 KB   0.0      3.5     0.1      0.5       0.6      0.1       0.0   2.2     31.2     55.6    115.01            109.53        29    3.966     51M  7353K       2.9       5.6

...

Completed overwrite (ID: ) in 289 seconds
ops/sec	mb/sec	Size-GB	L0_GB	Sum_GB	W-Amp	W-MB/s	usec/op	p50	p75	p99	p99.9	p99.99	Uptime	Stall-time	Stall%	Test	Date	Version	Job-ID
111784	44.8	0.0	0.5	2.2	2.0	9.2	285.9	215.3	264.4	1232	13299	23310	243	00:00:0.000	0.0	overwrite.t32.s0	2021-09-14T11:58:26.000-07:00	6.24
```

Reviewed By: zhichao-cao

Differential Revision: D30940352

Pulled By: ltamasi

fbshipit-source-id: ae7f5cd5440c8529788dda043266121fc2be0853

diff --git a/tools/benchmark.sh b/tools/benchmark.sh
index 185f4186e4204518934d478a90e2fa61ab664091..665990dfb0b5e2318f7f8a1e17620c3295616b84 100755 (executable)
--- a/tools/benchmark.sh
+++ b/tools/benchmark.sh
@@ -246,14 +246,7 @@ function summarize_result {
   l0_wgb=$( grep "^  L0" $test_out | tail -1 | awk '{ print $9 }' )
   sum_wgb=$( grep "^ Sum" $test_out | tail -1 | awk '{ print $9 }' )
   sum_size=$( grep "^ Sum" $test_out | tail -1 | awk '{ printf "%.1f", $3 / 1024.0 }' )
-  if [[ "$l0_wgb" == "" ]]; then
-      l0_wgb="0.0"
-  fi
-  if [[ "$l0_wgb" == "0.0" ]]; then
-      wamp="0.0"
-  else
-      wamp=$( echo "scale=1; $sum_wgb / $l0_wgb" | bc )
-  fi
+  wamp=$( grep "^ Sum" $test_out | tail -1 | awk '{ printf "%.1f", $12 }' )
   if [[ "$sum_wgb" == "" ]]; then
       wmb_ps=""
   else