From f5f69a3de9a3e0b8d4e211f155853a29cd400e92 Mon Sep 17 00:00:00 2001 From: Joe Tsai Date: Tue, 21 Oct 2025 15:11:32 -0700 Subject: [PATCH] encoding/json/jsontext: avoid pinning application data in pools MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Previously, we put a jsontext.Encoder (or Decoder) back into a pool with minimal reset logic. This was semantically safe since we always did a full reset after obtaining an Encoder/Decoder back out of the pool. However, this meant that so long as an Encoder/Decoder was alive in the pool, any application data referenced by the coder would be kept alive longer than necessary. Explicitly, clear such fields so that application data can be more aggressively garbage collected. Performance: name old time/op new time/op delta Unmarshal/Bool-32 52.0ns ± 3% 50.3ns ± 3% -3.30% (p=0.001 n=10+10) Marshal/Bool-32 55.4ns ± 3% 54.4ns ± 2% -1.75% (p=0.006 n=10+9) This only impacts the performance of discrete Marshal/Unmarshal calls. For the simplest possible call (i.e., to marsha/unmarshal a bool), there is a 1-2ns slow down. This is an appropriate slowdown for an improvement in memory utilization. Change-Id: I5e7d7827473773e53a9dcb3d7fe9052a75481e9f Reviewed-on: https://go-review.googlesource.com/c/go/+/713640 Reviewed-by: Damien Neil Reviewed-by: Johan Brandhorst-Satzkorn TryBot-Bypass: Damien Neil Reviewed-by: Dmitri Shuralyov Reviewed-by: Daniel Martí Auto-Submit: Damien Neil --- src/encoding/json/jsontext/pools.go | 12 ++++++++++++ src/encoding/json/v2/arshal.go | 1 + 2 files changed, 13 insertions(+) diff --git a/src/encoding/json/jsontext/pools.go b/src/encoding/json/jsontext/pools.go index 4f9e0ea410..3066ab4a1d 100644 --- a/src/encoding/json/jsontext/pools.go +++ b/src/encoding/json/jsontext/pools.go @@ -54,6 +54,10 @@ func getBufferedEncoder(opts ...Options) *Encoder { return e } func putBufferedEncoder(e *Encoder) { + if cap(e.s.availBuffer) > 64<<10 { + e.s.availBuffer = nil // avoid pinning arbitrarily large amounts of memory + } + // Recycle large buffers only if sufficiently utilized. // If a buffer is under-utilized enough times sequentially, // then it is discarded, ensuring that a single large buffer @@ -95,9 +99,14 @@ func getStreamingEncoder(w io.Writer, opts ...Options) *Encoder { } } func putStreamingEncoder(e *Encoder) { + if cap(e.s.availBuffer) > 64<<10 { + e.s.availBuffer = nil // avoid pinning arbitrarily large amounts of memory + } if _, ok := e.s.wr.(*bytes.Buffer); ok { + e.s.wr, e.s.Buf = nil, nil // avoid pinning the provided bytes.Buffer bytesBufferEncoderPool.Put(e) } else { + e.s.wr = nil // avoid pinning the provided io.Writer if cap(e.s.Buf) > 64<<10 { e.s.Buf = nil // avoid pinning arbitrarily large amounts of memory } @@ -126,6 +135,7 @@ func getBufferedDecoder(b []byte, opts ...Options) *Decoder { return d } func putBufferedDecoder(d *Decoder) { + d.s.buf = nil // avoid pinning the provided buffer bufferedDecoderPool.Put(d) } @@ -142,8 +152,10 @@ func getStreamingDecoder(r io.Reader, opts ...Options) *Decoder { } func putStreamingDecoder(d *Decoder) { if _, ok := d.s.rd.(*bytes.Buffer); ok { + d.s.rd, d.s.buf = nil, nil // avoid pinning the provided bytes.Buffer bytesBufferDecoderPool.Put(d) } else { + d.s.rd = nil // avoid pinning the provided io.Reader if cap(d.s.buf) > 64<<10 { d.s.buf = nil // avoid pinning arbitrarily large amounts of memory } diff --git a/src/encoding/json/v2/arshal.go b/src/encoding/json/v2/arshal.go index e26f3340ee..5537a467d8 100644 --- a/src/encoding/json/v2/arshal.go +++ b/src/encoding/json/v2/arshal.go @@ -571,5 +571,6 @@ func putStrings(s *stringSlice) { if cap(*s) > 1<<10 { *s = nil // avoid pinning arbitrarily large amounts of memory } + clear(*s) // avoid pinning a reference to each string stringsPools.Put(s) } -- 2.52.0