On Tue, 26 May 2026 20:14:14 GMT, Ashay Rane <[email protected]> wrote:
>> Prior to this patch, every HTTP request created a new 16KB buffer for >> encoding the header, which is typically only a few hundred bytes long. >> This increased pressure on the garbage collector when the client created >> lots of requests. This patch instead makes the header encoder reuse the >> buffer that is created during the handling of the first request. >> >> The caveat, however, is that the downstream consumers of the header are >> asynchronous, so the encoder needs to take special care to ensure that >> it doesn't modify or invalidate the buffer after it hands the buffer >> over to the downstream asynchronous pipeline. To resolve this, this >> patch snapshots the buffer data into compact copies sized to the actual >> encoded length. Doing so makes the buffer immediately available for >> reuse via `clear()` and `limit()`. >> >> For typical requests, this reduces per-request allocation from 16KB to >> a few hundred bytes (i.e. the size of the compact copy of the encoded >> headers), with the 16KB encoding buffer allocated once per connection >> instead of once per request. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Ashay Rane has updated the pull request incrementally with one additional > commit since the last revision: > > Address PR comments > > 1. Mark newly-introduced package private functions (`getConnections()` > and `getCachedHeaderBuffer()`) so that it's clear that they're used > only by the tests. > > 2. Early return in `getHeaderBuffer()` when `cachedHeaderBuffer` is > newly allocated, thus skipping the `clear()` and `limit()` calls. test/jdk/java/net/httpclient/http2/HeaderEncodingBufferReuseTest.java line 96: > 94: .build()) { > 95: > 96: // Force a large cached header buffer by sending 300 headers. The `bufferSize` of the cached buffer in the `Http2Connection` isn't decided by the number of headers. Instead, from what I see in `Http2Connection.encodeHeaders()` it's (almost fixed) size decided by the connection settings and a HttpClient configuration: int bufferSize = Math.min(Math.max(getMaxSendFrameSize(), 1024), DEFAULT_FRAME_SIZE); So this comment here is misleading and in fact it doesn't need creation of 300 odd headers to test the change. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/30931#discussion_r3309321276
