Le 19/08/2022 à 00:33, Jean Abou Samra a écrit :
Le 19/08/2022 à 00:18, Jean Abou Samra a écrit :
Calling the Guile compiler often causes this BDWGC error: “Too
many root sets”.
scheme@(guile-user)> (define-syntax-rule (repeat n expr expr* ...)
(do ((i 0 (1+ i))) ((eqv? i n)) expr expr* ...))
scheme@(guile-user)> (use-modules (system base compile))
scheme@(guile-user)> (repeat 10000 (compile 5))
Too many root sets
Abandon (core dumped)
Any idea what is going on here? Should I report it as a bug?
Is there a workaround?
Interestingly:
scheme@(guile-user)> (define-syntax-rule (repeat n expr expr* ...) (do
((i 0 (1+ i))) ((eqv? i n)) expr expr* ...))
scheme@(guile-user)> (use-modules (system base compile))
scheme@(guile-user)> (repeat 10000 (compile 5 #:to 'bytecode))
scheme@(guile-user)> (use-modules (system vm loader))
scheme@(guile-user)> (repeat 10000 (load-thunk-from-memory (compile 5
#:to 'bytecode)))
Too many root sets
Abandon (core dumped)
So the problem lies in the VM loading infrastructure. (This is
as far as I can investigate for now.)
I tried this code:
(use-modules (system vm loader))
(define-syntax-rule (repeat n-expr expr expr* ...)
(let ((n n-expr))
(do ((i 0 (1+ i)))
((eqv? i n))
expr expr* ...)))
(let ((code (compile 5 #:to 'bytecode)))
(repeat 10000
(load-thunk-from-memory code)
(display (length (all-mapped-elf-images))) (newline)))
For me, the output ends with
8174
8175
8176
8177
8178
8179
8180
8181
Too many root sets
Abandon (core dumped)
Now, BDWGC defines MAX_ROOT_SETS in include/private/gc_priv.h as
/* Root sets. Logically private to mark_rts.c. But we don't want the */
/* tables scanned, so we put them here. */
/* MAX_ROOT_SETS is the maximum number of ranges that can be */
/* registered as static roots. */
# ifdef LARGE_CONFIG
# define MAX_ROOT_SETS 8192
# elif !defined(SMALL_CONFIG)
# define MAX_ROOT_SETS 2048
# else
# define MAX_ROOT_SETS 512
# endif
I am using Fedora, where BDWGC is compiled with --enable-large-config. When
the loader ingests a VM code chunk, it does (loader.c)
if (gc_root)
GC_add_roots (gc_root, gc_root + gc_root_size);
So each load is really adding a root until this threshold of 8192
is crossed.
I have no idea if it is possible to fix and/or work around this
other than by not calling compile often like this.
(Yes, I know, I should be using eval for one-off code evaluation,
but it discards source locations, which is what brought me here
in the first place.)
Jean