Avoid MimeType garbage creation #22340
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in: web
Issues in web modules (web, webmvc, webflux, websocket)
type: enhancement
A general enhancement
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bclozel
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jhoeller
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Feb 5, 2019
bclozel
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Jun 28, 2019
As of gh-22340, `MimeTypeUtils` has a built-in LRU cache implementation for caching parsed MIME types and avoiding excessive garbage creation at runtime. This implementation, when hit with highly concurrent reads on the same media type (the cache key), can create multiple keys for the same MIME type string. This duplication leads to the cache filling up and evicting entries. When the cache fetches a duplicate key, it is then not associated with a value and the cache can return a `null` value, which is forbidden by the API contract. This commit adds another cache check within the write lock: this avoids creating duplicate entries in the cache and `null` return values. Fixes gh-23211
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While profiling Spring web applications (MVC and WebFlux), it seems that
MimeType(throughMediaType) is creating a significant amount of garbage that could be avoided.toString()result ofMimeTypeinstances, since it cannot change and this method is called many times on hot pathsMediaType.parseMediaTypeis called multiple times, for each request; this could be backed by a simple LRU cache implementation to avoid re-parsing known media typesMimeTypeUtils.parseMimeTypeparsing code can be improved; a draft implementation shows +40% throughput and -10% allocation.MimeTypeUtilsandMediaTypeboth have static sections where well-known types are parsed; changing those fromAPPLICATION_JSON = MimeType.valueOf(APPLICATION_JSON_VALUE);toAPPLICATION_JSON = new MimeType("application", "json");leads to a bit of duplication but consistently reduces garbage and CPU usage at startup time (approx. 10ms).The text was updated successfully, but these errors were encountered: