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342391f39d
This upgrades the version of Ormolu required by the HGE repository to v0.5.0.1, and reformats all code accordingly. Ormolu v0.5 reformats code that uses infix operators. This is mostly useful, adding newlines and indentation to make it clear which operators are applied first, but in some cases, it's unpleasant. To make this easier on the eyes, I had to do the following: * Add a few fixity declarations (search for `infix`) * Add parentheses to make precedence clear, allowing Ormolu to keep everything on one line * Rename `relevantEq` to `(==~)` in #6651 and set it to `infix 4` * Add a few _.ormolu_ files (thanks to @hallettj for helping me get started), mostly for Autodocodec operators that don't have explicit fixity declarations In general, I think these changes are quite reasonable. They mostly affect indentation. PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6675 GitOrigin-RevId: cd47d87f1d089fb0bc9dcbbe7798dbceedcd7d83
79 lines
3.3 KiB
Haskell
79 lines
3.3 KiB
Haskell
module Hasura.GC
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( ourIdleGC,
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)
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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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--
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-- NOTE: as always the cost of a major GC (forced here, or initiated by the RTS)
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-- with the default copying collector is proportional to live (non-garbage)
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-- heap data. Tune parameters here to balance: more frequent GC pauses vs.
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-- prompt cleanup of foreign data (which does not exert GC pressure).
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--
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-- NOTE: larger nursery size (+RTS -A) may help us run more finalizers during
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-- cheaper minor GCs, before they are promoted, making it feasible (maybe) to
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-- run this with longer interval parameters.
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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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