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This commit applies ormolu to the whole Haskell code base by running `make format`. For in-flight branches, simply merging changes from `main` will result in merge conflicts. To avoid this, update your branch using the following instructions. Replace `<format-commit>` by the hash of *this* commit. $ git checkout my-feature-branch $ git merge <format-commit>^ # and resolve conflicts normally $ make format $ git commit -a -m "reformat with ormolu" $ git merge -s ours post-ormolu https://github.com/hasura/graphql-engine-mono/pull/2404 GitOrigin-RevId: 75049f5c12f430c615eafb4c6b8e83e371e01c8e
67 lines
2.8 KiB
Haskell
67 lines
2.8 KiB
Haskell
module Hasura.GC where
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import Control.Concurrent.Extended qualified as C
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import GHC.Stats
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import Hasura.Logging
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import Hasura.Prelude
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import System.Mem (performMajorGC)
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-- | The RTS's idle GC doesn't work for us:
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--
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-- - when `-I` is too low it may fire continuously causing scary high CPU
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-- when idle among other issues (see #2565)
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-- - when we set it higher it won't run at all leading to memory being
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-- retained when idle (especially noticeable when users are benchmarking and
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-- see memory stay high after finishing). In the theoretical worst case
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-- there is such low haskell heap pressure that we never run finalizers to
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-- free the foreign data from e.g. libpq.
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-- - as of GHC 8.10.2 we have access to `-Iw`, but those two knobs still
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-- don’t give us a guarantee that a major GC will always run at some
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-- minumum frequency (e.g. for finalizers)
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--
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-- ...so we hack together our own using GHC.Stats, which should have
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-- insignificant runtime overhead.
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ourIdleGC ::
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Logger Hasura ->
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-- | Run a major GC when we've been "idle" for idleInterval
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DiffTime ->
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-- | ...as long as it has been > minGCInterval time since the last major GC
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DiffTime ->
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-- | Additionally, if it has been > maxNoGCInterval time, force a GC regardless.
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DiffTime ->
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IO void
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ourIdleGC (Logger logger) idleInterval minGCInterval maxNoGCInterval =
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startTimer >>= go 0 0
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where
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go gcs_prev major_gcs_prev timerSinceLastMajorGC = do
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timeSinceLastGC <- timerSinceLastMajorGC
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when (timeSinceLastGC < minGCInterval) $ do
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-- no need to check idle until we've passed the minGCInterval:
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C.sleep (minGCInterval - timeSinceLastGC)
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RTSStats {gcs, major_gcs} <- getRTSStats
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-- We use minor GCs as a proxy for "activity", which seems to work
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-- well-enough (in tests it stays stable for a few seconds when we're
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-- logically "idle" and otherwise increments quickly)
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let areIdle = gcs == gcs_prev
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areOverdue = timeSinceLastGC > maxNoGCInterval
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-- a major GC was run since last iteration (cool!), reset timer:
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if
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| major_gcs > major_gcs_prev -> do
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startTimer >>= go gcs major_gcs
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-- we are idle and its a good time to do a GC, or we're overdue and must run a GC:
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| areIdle || areOverdue -> do
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when (areOverdue && not areIdle) $
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logger $
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UnstructuredLog LevelWarn $
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"Overdue for a major GC: forcing one even though we don't appear to be idle"
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performMajorGC
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startTimer >>= go (gcs + 1) (major_gcs + 1)
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-- else keep the timer running, waiting for us to go idle:
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| otherwise -> do
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C.sleep idleInterval
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go gcs major_gcs timerSinceLastMajorGC
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