perf(startup): use WAL journal for sqlite databases in DENO_DIR

[piscisaureus]

While investigating poor cold start performance on my GCP VM (32 cores, 130GB SSD), I found that writing to the various sqlite databases in DENO_DIR was quite slow. The slowness seems to primarily be caused by excessive latency from a number of fsync() calls.

The performance difference is best demonstrated by deleting the sqlite databases from DENO_DIR while leaving the downloaded sources in place.

The benchmark (see notes below):

piscisaureus@bert-us:~/erofs/source$ export DENO_DIR=./.deno
piscisaureus@bert-us:~/erofs/source$ hyperfine --warmup 3   \
  --prepare "rm -rf .deno/*_v1*"                            \
  "deno run -A --cached-only demo.ts"                       \
  "eatmydata deno run -A --cached-only demo.ts"             \
  "~/deno/target/release/deno run -A --cached-only demo.ts"
Benchmark 1: deno run -A --cached-only demo.ts
  Time (mean ± σ):      1.174 s ±  0.037 s    [User: 0.153 s, System: 0.184 s]
  Range (min … max):    1.104 s …  1.212 s    10 runs
 
Benchmark 2: eatmydata deno run -A --cached-only demo.ts
  Time (mean ± σ):     265.5 ms ±   3.6 ms    [User: 138.5 ms, System: 135.1 ms]
  Range (min … max):   260.6 ms … 271.2 ms    11 runs
 
Benchmark 3: ~/deno/target/release/deno run -A --cached-only demo.ts
  Time (mean ± σ):     226.2 ms ±   9.2 ms    [User: 136.7 ms, System: 93.3 ms]
  Range (min … max):   218.8 ms … 247.1 ms    13 runs
 
Summary
  ~/deno/target/release/deno run -A --cached-only demo.ts ran
    1.17 ± 0.05 times faster than eatmydata deno run -A --cached-only demo.ts
    5.19 ± 0.27 times faster than deno run -A --cached-only demo.ts

Notes:

• Benchmark 1: unmodified Deno 1.43.6
• Benchmark 2: unmodified Deno 1.43.6 wrapped with eatmydata (which is a tool to neuter fsync() calls)
• Benchmark 3: this PR applied on top of Deno 1.43.6

The script that got benchmarked:

// demo.ts
import * as express from "npm:express@4.16.3";
import * as postgres from "https://deno.land/x/postgres/mod.ts";

let _dummy = [express, postgres]; // Force use of imports.
console.log("hello world");

[dsherret]

It seems we previously disabled this for performance reasons? #18084

I wonder what impact this will have on non-gcp machines (not sure why that machine is so slow because neither my winows, mac, or linux machine have this issue)

[dsherret]

Oh, just realized that was done only for startup perf reasons, but we initialize the sqlite caches on blocking threads now.

[mmastrac]

I think that was in #18401, and we benchmarked almost all of them within a 10th of a ms.

[dsherret]

I just benchmarked WAL and it is much faster on my mac. 176ms down to 142ms.

[dsherret]

LGTM

[littledivy]

LGTM!