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Slow creation of vm contexts in Node 8 #14229
Description
- Version:
v8.1.4 - Platform:
Linux stbx-frontend-dev 3.13.0-35-generic #62-Ubuntu SMP Fri Aug 15 01:58:42 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux - Subsystem: VM
It looks like process of creating new contexts got much slower in recent nodejs release.
Consider following example:
const vm = require('vm');
for (let i = 0; i < 10; i++) {
const execStart = process.hrtime();
vm.runInNewContext('', {});
const execEnd = process.hrtime(execStart);
console.log(`${execEnd[0]}s ${execEnd[1] / 1000000}ms`);
}Here we're creating new context for each run and executing empty code string.
Output for nodejs 8.1.4:
0s 15.532509ms
0s 16.45096ms
0s 14.373037ms
0s 19.49953ms
0s 15.372955ms
0s 15.158201ms
0s 17.679574ms
0s 14.971238ms
0s 15.189564ms
0s 15.245761ms
Output for nodejs 6:
0s 1.963924ms
0s 0.963834ms
0s 1.03562ms
0s 0.874986ms
0s 0.821775ms
0s 0.795037ms
0s 0.692259ms
0s 0.675377ms
0s 0.703469ms
0s 0.707926ms
However, if we're reusing one context instead of creating new ones (like this), everything except first run is ok in nodejs 8 too:
0s 20.257369ms
0s 0.068348ms
0s 0.052941ms
0s 0.0222ms
0s 0.028692ms
0s 0.021334ms
0s 0.021695ms
0s 0.029571ms
0s 0.019861ms
0s 0.020045ms
Basically, slow part is vm.createContext, code execution speed itself is fine (benchmark with just vm.createContext({}) shows similar timings).
It looks like this problem exists only on Linux (node v8.1.2 on Darwin resure-osx 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64 is as fast as node 6).
Activity
bnoordhuis commentedon Jul 14, 2017
Thanks for the bug report but this is a known issue that is currently under discussion in #14171. It's caused by the disabling of snapshots in the recent security release.
AurelienRibon commentedon Aug 16, 2017
I don't want to be the sad party guy, but with node 8.4 we still get the same results as 8.1 for the test mentioned in this issue. I'm not sure we can consider this issue as closed. Can you update the status? Do we need to manually enable the snapshots?
TimothyGu commentedon Aug 17, 2017
I can reproduce this.
On 8.1.2:
On 8.2.1:
On 8.4.0:
TimothyGu commentedon Aug 17, 2017
Seems like it was a bug in our build system that caused this :(
It will be fixed in #14875.
addaleax commentedon Aug 17, 2017
I am almost certain this is because of #14875, so I think this can be closed as a duplicate of #14870 (or, technically, that one is a duplicate of this one, but, you know, it doesn’t really matter and the PR has the
Fixes:tag for the other issue).