diff options
| -rw-r--r-- | Changes | 4 | ||||
| -rw-r--r-- | man/ocamlrun.m | 3 | ||||
| -rw-r--r-- | manual/src/cmds/runtime.etex | 3 | ||||
| -rw-r--r-- | runtime/caml/config.h | 2 | ||||
| -rw-r--r-- | runtime/freelist.c | 2 | ||||
| -rw-r--r-- | stdlib/gc.mli | 21 |
6 files changed, 15 insertions, 20 deletions
@@ -49,6 +49,10 @@ Working version - #10136: Minor clean-ups in runtime/io.c and runtime/caml/io.h (Xavier Leroy, review by David Allsopp and Guillaume Munch-Maccagnoni) +- #10188: Switch the default allocation policy to best-fit and adjust the + default overhead parameter accordingly. + (Damien Doligez, review by Josh Berdine and Xavier Leroy) + ### Code generation and optimizations: - #9876: do not cache the young_limit GC variable in a processor register. diff --git a/man/ocamlrun.m b/man/ocamlrun.m index ba59d20b7f..7c4734bb4c 100644 --- a/man/ocamlrun.m +++ b/man/ocamlrun.m @@ -151,8 +151,7 @@ The initial size of the major heap (in words). .BR a \ (allocation_policy) The policy used for allocating in the OCaml heap. Possible values are 0 for the next-fit policy, 1 for the first-fit -policy, and 2 for the best-fit policy. Best-fit is still experimental, -but probably the best of the three. The default is 0. +policy, and 2 for the best-fit policy. The default is 2. See the Gc module documentation for details. .TP .BR s \ (minor_heap_size) diff --git a/manual/src/cmds/runtime.etex b/manual/src/cmds/runtime.etex index a204598a48..4806d5f984 100644 --- a/manual/src/cmds/runtime.etex +++ b/manual/src/cmds/runtime.etex @@ -140,8 +140,7 @@ The following environment variables are also consulted: \item[a] ("allocation_policy") The policy used for allocating in the OCaml heap. Possible values are "0" for the next-fit policy, "1" for the first-fit - policy, and "2" for the best-fit policy. Best-fit is still experimental, - but probably the best of the three. The default is "0" (next-fit). + policy, and "2" for the best-fit policy. The default is "2" (best-fit). See the Gc module documentation for details. \item[s] ("minor_heap_size") Size of the minor heap. (in words) \item[i] ("major_heap_increment") Default size increment for the diff --git a/runtime/caml/config.h b/runtime/caml/config.h index 5e06f022b6..9445e36001 100644 --- a/runtime/caml/config.h +++ b/runtime/caml/config.h @@ -240,7 +240,7 @@ typedef uint64_t uintnat; /* Default speed setting for the major GC. The heap will grow until the dead objects and the free list represent this percentage of the total size of live objects. */ -#define Percent_free_def 80 +#define Percent_free_def 120 /* Default setting for the compacter: 500% (i.e. trigger the compacter when 5/6 of the heap is free or garbage) diff --git a/runtime/freelist.c b/runtime/freelist.c index e018df7129..ae047081f4 100644 --- a/runtime/freelist.c +++ b/runtime/freelist.c @@ -1755,7 +1755,7 @@ enum { policy_best_fit = 2, }; -uintnat caml_allocation_policy = policy_next_fit; +uintnat caml_allocation_policy = policy_best_fit; /********************* exported functions *****************************/ diff --git a/stdlib/gc.mli b/stdlib/gc.mli index ab615c3cc3..12d3984d03 100644 --- a/stdlib/gc.mli +++ b/stdlib/gc.mli @@ -108,7 +108,7 @@ type control = percentage of the memory used for live data. The GC will work more (use more CPU time and collect blocks more eagerly) if [space_overhead] is smaller. - Default: 80. *) + Default: 100. *) mutable verbose : int; [@ocaml.deprecated_mutable "Use {(Gc.get()) with Gc.verbose = ...}"] @@ -164,30 +164,23 @@ type control = memory than both next-fit and first-fit. (since OCaml 4.10) - The current default is next-fit, as the best-fit policy is new - and not yet widely tested. We expect best-fit to become the - default in the future. + The default is best-fit. On one example that was known to be bad for next-fit and first-fit, next-fit takes 28s using 855Mio of memory, first-fit takes 47s using 566Mio of memory, best-fit takes 27s using 545Mio of memory. - Note: When changing to a low-fragmentation policy, you may - need to augment the [space_overhead] setting, for example - using [100] instead of the default [80] which is tuned for - next-fit. Indeed, the difference in fragmentation behavior - means that different policies will have different proportion - of "wasted space" for a given program. Less fragmentation - means a smaller heap so, for the same amount of wasted space, - a higher proportion of wasted space. This makes the GC work - harder, unless you relax it by increasing [space_overhead]. + Note: If you change to next-fit, you may need to reduce + the [space_overhead] setting, for example using [80] instead + of the default [100] which is tuned for best-fit. Otherwise, + your program will need more memory. Note: changing the allocation policy at run-time forces a heap compaction, which is a lengthy operation unless the heap is small (e.g. at the start of the program). - Default: 0. + Default: 2. @since 3.11.0 *) |