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bug#46326: 27.1.50; Excessive memory allocations with minibuffer-with-se
From: |
Stefan Monnier |
Subject: |
bug#46326: 27.1.50; Excessive memory allocations with minibuffer-with-setup-hook |
Date: |
Fri, 23 Apr 2021 14:26:57 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
> I have an issue on 27.1.50 with excessive memory allocations when using
> minibuffer-with-setup-hook with large closures and :append.
Indeed, we have a problem there. I think it's fairly hard to fix it
for good without introducing incompatibilities, because `add-hook` has
been defined to compare its functions with `equal` "for ever" and
changing it to use `eq` or `function-equal` will inevitably break
code out there in subtle ways.
IOW I think the better fix is to change `minibuffer-with-setup-hook` to
use an indirection via a symbol.
As for reducing the impact of the underlying issue, I see we could
reduce the amount of `equal` tests being performed, by using `eq` for
the lookups in `hook--depth-alist`.
So before we install the "real" solution, could you try the patch below
and report how much it helps (if at all)?
Stefan
diff --git a/lisp/subr.el b/lisp/subr.el
index c2be26a15f5..7b718a48a8d 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1830,12 +1834,13 @@ add-hook
(unless (member function hook-value)
(when (stringp function) ;FIXME: Why?
(setq function (purecopy function)))
+ ;; All those `equal' tests performed between functions can end up being
+ ;; costly since those functions may be large recursive and even cyclic
+ ;; structures, so we index `hook--depth-alist' with `eq'. (bug#46326)
(when (or (get hook 'hook--depth-alist) (not (zerop depth)))
;; Note: The main purpose of the above `when' test is to avoid running
;; this `setf' before `gv' is loaded during bootstrap.
- (setf (alist-get function (get hook 'hook--depth-alist)
- 0 'remove #'equal)
- depth))
+ (push (cons function depth) (get hook 'hook--depth-alist)))
(setq hook-value
(if (< 0 depth)
(append hook-value (list function))
@@ -1845,8 +1850,8 @@ add-hook
(setq hook-value
(sort (if (< 0 depth) hook-value (copy-sequence hook-value))
(lambda (f1 f2)
- (< (alist-get f1 depth-alist 0 nil #'equal)
- (alist-get f2 depth-alist 0 nil #'equal))))))))
+ (< (alist-get f1 depth-alist 0 nil #'eq)
+ (alist-get f2 depth-alist 0 nil #'eq))))))))
;; Set the actual variable
(if local
(progn
@@ -1907,11 +1912,20 @@ remove-hook
(not (and (consp (symbol-value hook))
(memq t (symbol-value hook)))))
(setq local t))
- (let ((hook-value (if local (symbol-value hook) (default-value hook))))
+ (let ((hook-value (if local (symbol-value hook) (default-value hook)))
+ (old-fun nil))
;; Remove the function, for both the list and the non-list cases.
(if (or (not (listp hook-value)) (eq (car hook-value) 'lambda))
- (if (equal hook-value function) (setq hook-value nil))
- (setq hook-value (delete function (copy-sequence hook-value))))
+ (when (equal hook-value function)
+ (setq old-fun hook-value)
+ (setq hook-value nil))
+ (when (setq old-fun (car (member function hook-value)))
+ (setq hook-value (remq old-fun hook-value))))
+ (when old-fun
+ ;; Remove auxiliary depth info to avoid leaks.
+ (put hook 'hook--depth-alist
+ (delq (assq old-fun (get hook 'hook--depth-alist))
+ (get hook 'hook--depth-alist))))
;; If the function is on the global hook, we need to shadow it locally
;;(when (and local (member function (default-value hook))
;; (not (member (cons 'not function) hook-value)))
- bug#46326: 27.1.50; Excessive memory allocations with minibuffer-with-setup-hook,
Stefan Monnier <=