reduce the number of write syscalls by buffering

[sokra]

buffer the output of bfj to avoid 1000s of small write calls

[ijjk]

Stats from current PR

Default Server Mode (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
buildDuration	13s	12.5s	-471ms
nodeModulesSize	46.7 MB	46.7 MB	⚠️ +2.99 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.726	2.729	0
/ avg req/sec	916.99	915.94	⚠️ -1.05
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.627	1.543	-0.08
/error-in-render avg req/sec	1536.82	1620.57	+83.75

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
677f882d2ed8..e6c6.js gzip	13.4 kB	13.4 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-HASH.js gzip	7.12 kB	7.12 kB	✓
webpack-HASH.js gzip	751 B	751 B	✓
Overall change	60.2 kB	60.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
polyfills-HASH.js gzip	31.3 kB	31.3 kB	✓
Overall change	31.3 kB	31.3 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_app-8fbabfc..6440.js gzip	1.28 kB	1.28 kB	✓
_error-d07ca..ef4d.js gzip	3.71 kB	3.71 kB	✓
amp-9716187d..0aa8.js gzip	536 B	536 B	✓
hooks-107e90..74c7.js gzip	888 B	888 B	✓
index-ac435c..ecf2.js gzip	227 B	227 B	✓
link-c31053f..c329.js gzip	1.64 kB	1.64 kB	✓
routerDirect..dc9d.js gzip	303 B	303 B	✓
withRouter-6..0e02.js gzip	302 B	302 B	✓
Overall change	8.89 kB	8.89 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_buildManifest.js gzip	371 B	371 B	✓
Overall change	371 B	371 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
index.html gzip	612 B	612 B	✓
link.html gzip	620 B	620 B	✓
withRouter.html gzip	607 B	607 B	✓
Overall change	1.84 kB	1.84 kB	✓

---

Serverless Mode

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
buildDuration	15s	14.8s	-184ms
nodeModulesSize	46.7 MB	46.7 MB	⚠️ +2.99 kB

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
677f882d2ed8..e6c6.js gzip	13.4 kB	13.4 kB	✓
framework.HASH.js gzip	39 kB	39 kB	✓
main-HASH.js gzip	7.12 kB	7.12 kB	✓
webpack-HASH.js gzip	751 B	751 B	✓
Overall change	60.2 kB	60.2 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
polyfills-HASH.js gzip	31.3 kB	31.3 kB	✓
Overall change	31.3 kB	31.3 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_app-8fbabfc..6440.js gzip	1.28 kB	1.28 kB	✓
_error-d07ca..ef4d.js gzip	3.71 kB	3.71 kB	✓
amp-9716187d..0aa8.js gzip	536 B	536 B	✓
hooks-107e90..74c7.js gzip	888 B	888 B	✓
index-ac435c..ecf2.js gzip	227 B	227 B	✓
link-c31053f..c329.js gzip	1.64 kB	1.64 kB	✓
routerDirect..dc9d.js gzip	303 B	303 B	✓
withRouter-6..0e02.js gzip	302 B	302 B	✓
Overall change	8.89 kB	8.89 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_buildManifest.js gzip	371 B	371 B	✓
Overall change	371 B	371 B	✓

Serverless bundles

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_error.js	1.37 MB	1.37 MB	✓
404.html	2.67 kB	2.67 kB	✓
500.html	2.65 kB	2.65 kB	✓
amp.amp.html	10.7 kB	10.7 kB	✓
amp.html	1.86 kB	1.86 kB	✓
hooks.html	1.92 kB	1.92 kB	✓
index.js	1.37 MB	1.37 MB	✓
link.js	1.42 MB	1.42 MB	✓
routerDirect.js	1.42 MB	1.42 MB	✓
withRouter.js	1.42 MB	1.42 MB	✓
Overall change	7.01 MB	7.01 MB	✓

---

Webpack 5 Mode (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
buildDuration	15.5s	15.5s	⚠️ +85ms
nodeModulesSize	46.7 MB	46.7 MB	⚠️ +2.99 kB

Page Load Tests Overall increase ✓

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.708	2.73	⚠️ +0.02
/ avg req/sec	923.02	915.72	⚠️ -7.3
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.606	1.523	-0.08
/error-in-render avg req/sec	1556.8	1641.84	+85.04

Client Bundles (main, webpack, commons)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
597-3f457946..288d.js gzip	13.3 kB	13.3 kB	✓
778-9356d64c..e712.js gzip	7.05 kB	7.05 kB	✓
framework.HASH.js gzip	39.3 kB	39.3 kB	✓
main-HASH.js gzip	151 B	151 B	✓
webpack-HASH.js gzip	993 B	993 B	✓
Overall change	60.8 kB	60.8 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
polyfills-HASH.js gzip	31.1 kB	31.1 kB	✓
Overall change	31.1 kB	31.1 kB	✓

Client Pages

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_app-5cc66b2..6f03.js gzip	1.3 kB	1.3 kB	✓
_error-55112..054d.js gzip	3.68 kB	3.68 kB	✓
amp-89a5460c..567f.js gzip	558 B	558 B	✓
hooks-8c2e74..be37.js gzip	924 B	924 B	✓
index-fec729..83b2.js gzip	243 B	243 B	✓
link-dd34d9b..0ade.js gzip	1.66 kB	1.66 kB	✓
routerDirect..5759.js gzip	336 B	336 B	✓
withRouter-1..98bf.js gzip	334 B	334 B	✓
Overall change	9.03 kB	9.03 kB	✓

Client Build Manifests

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
_buildManifest.js gzip	349 B	349 B	✓
Overall change	349 B	349 B	✓

Rendered Page Sizes

	vercel/next.js canary	vercel/next.js bugfix/write-count	Change
index.html gzip	610 B	610 B	✓
link.html gzip	616 B	616 B	✓
withRouter.html gzip	606 B	606 B	✓
Overall change	1.83 kB	1.83 kB	✓

Diffs

Diff for index.html

@@ -43,7 +43,7 @@
         "props": { "pageProps": {} },
         "page": "/",
         "query": {},
-        "buildId": "_OSrKjLtgVa4w19PGEl5k",
+        "buildId": "RCawA1U20KBUbLsAj-c36",
         "isFallback": false,
         "gip": true
       }
@@ -77,11 +77,11 @@
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_buildManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_buildManifest.js"
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_ssgManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_ssgManifest.js"
       async=""
     ></script>
   </body>

Diff for link.html

@@ -48,7 +48,7 @@
         "props": { "pageProps": {} },
         "page": "/link",
         "query": {},
-        "buildId": "_OSrKjLtgVa4w19PGEl5k",
+        "buildId": "RCawA1U20KBUbLsAj-c36",
         "isFallback": false,
         "gip": true
       }
@@ -82,11 +82,11 @@
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_buildManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_buildManifest.js"
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_ssgManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_ssgManifest.js"
       async=""
     ></script>
   </body>

Diff for withRouter.html

@@ -43,7 +43,7 @@
         "props": { "pageProps": {} },
         "page": "/withRouter",
         "query": {},
-        "buildId": "_OSrKjLtgVa4w19PGEl5k",
+        "buildId": "RCawA1U20KBUbLsAj-c36",
         "isFallback": false,
         "gip": true
       }
@@ -77,11 +77,11 @@
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_buildManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_buildManifest.js"
       async=""
     ></script>
     <script
-      src="/_next/static/_OSrKjLtgVa4w19PGEl5k/_ssgManifest.js"
+      src="/_next/static/RCawA1U20KBUbLsAj-c36/_ssgManifest.js"
       async=""
     ></script>
   </body>

Commit: 285378f