#13246: hPutBuf issues unnecessary empty write syscalls for large writes -------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Runtime System | Version: 8.0.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #13245 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nh2): When writing the fix, I noticed that my description of what exactly is the bug is wrong. The `if (size - w > count)` isn't the problem, that's just another infelicity (e.g. it'll make that if you have an 8 K buffer and write 2 K chunks to it, we'll always flush 6 K buffers), which I'll fix too. The real bug is simply that we `flushWriteBuffer` even if `w == 0` (handle buffer is empty). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13246#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler