Ludovic Courtès <ludo@gnu.org> skribis:

> #104 0x00007fc5247f3a92 in scm_hash_fn_ref () from /gnu/store/r658y3cgpnf99nxjxqgjiaizx20ac4k0-guile-2.2.4/lib/libguile-2.2.so.1
> #105 0x00007fc524859715 in vm_regular_engine () from /gnu/store/r658y3cgpnf99nxjxqgjiaizx20ac4k0-guile-2.2.4/lib/libguile-2.2.so.1
> #106 0x00007fc52485cd6a in scm_call_n () from /gnu/store/r658y3cgpnf99nxjxqgjiaizx20ac4k0-guile-2.2.4/lib/libguile-2.2.so.1
> #107 0x00007fc5247e0da7 in scm_primitive_eval () from /gnu/store/r658y3cgpnf99nxjxqgjiaizx20ac4k0-guile-2.2.4/lib/libguile-2.2.so.1
>
>
> and with debugging symbols:
>
> #3  0x00007fc5247ddc23 in scm_equal_p (x=x@entry="/gnu/store/djh3drjx3hnxlx1bsdnixdm3xjbg5v2c-guile-bootstrap-2.0/bin/guile", 
>     y=y@entry="/gnu/store/djh3drjx3hnxlx1bsdnixdm3xjbg5v2c-guile-bootstrap-2.0/bin/guile") at eq.c:290
> #4  0x00007fc52484891b in scm_i_struct_equalp (s1="#<struct <derivation>>" = {...}, s2="#<struct <derivation>>" = {...}) at struct.c:693
> #5  0x00007fc52484891b in scm_i_struct_equalp (s1="#<struct <derivation-input>>" = {...}, s2="#<struct <derivation-input>>" = {...}) at struct.c:693
> #6  0x00007fc5247ddc82 in scm_equal_p (
>     x=(#<struct <derivation-input> #<struct <derivation> (("out" . #<struct <derivation-output> "/gnu/store/jc5q4i55hrilibrmacs38skk3cpg2zyb-glibc-bootstrap-0" #f #f #f 3ade740>)) (#<struct <derivation-input> #<struct <derivation> (("out" . #<struct <derivation-output> "/gnu/store/nbi0mzk1dw37nnnahw9akn3bwzwi4gdk-module-import-compiled" #f #f #f 3ae6e00>)) (#<struct <derivation-input> #<struct <derivation> (("out" . #<struct <derivation-output> "/gnu/store/djh3drjx3hnxlx1bsdnixdm3xjbg5v2c-guile-bootstrap-2.0" #f #f #f 3af1b40>)) (#<struct <derivation-input> #<struct <derivation> (("out" . #<struct <derivation-output> "/gnu/store/dgncc5wmw8prxq09y71hqjc6g7rxqvvb-guile-2.0.9.tar.xz" sha256 #vu8(183 87 205 70 191 19 236 172 131 251 142 149 95 181 0 150 172 45 23 187 97 12 168 235 129 111 41 48 42 0 168 70) #f 3af10c0>)) () ("/gnu/store/7f1alh9qj2h0wwy2220npgnmw6pbrkwx-mirrors" "/gnu/store/vwyxp1dq4lb97n6b20w5cqxasy2dai79-content-addressed-mirrors") "i686-linux" "builtin:download" () (("content-addressed-mirrors" . "/gnu/store/vwyxp1dq4lb97n6b20w5cqxasy2dai79-content-addressed-mirrors") ("impureEnvVars" . "http_proxy https_proxy LC_ALL LC_MESSAGES LANG COLUMNS") ("mirrors" . "/gnu/store/7f1alh9qj2h0wwy2220npgnmw6pbrkwx-mirrors") ("out" . "/gnu/store/dgncc5wmw8prxq09y71hqjc6g7rxqvvb-guile-2.0.9.tar.xz") ("preferLocalBuild" . "1") ("url" . "(\"https://alpha.gnu.org/gnu/guix/bootstrap/i686-linux/20131110/guile-2.0.9.tar.xz\" \"http://alpha.gnu.org/gnu/guix/bootstrap/i686-linux/20131110/guile-2.0.9.tar.xz\" \"ftp://alpha.gnu.org/gnu/guix/bootstrap/i686-linux/20131110/guile-2.0.9.tar.xz\" \"http://www.fdn.fr/~lcourtes/software/guix/packages/i686-linux/20131110/guile-2.0.9.tar.xz\" \"http://flashner.co.il/guix/bootstrap/i686-linux/20131110/guile-2.0.9.tar.xz\")")) "/gnu/store/jagg4l53ar1m4hsgqlpisw9i4rq2whzd-guile-2.0.9.tar.xz.drv" 3af14e0> ("out") 3af1780>) ("/gnu/store/d32948vi9bs5mmbnvlczqcgwwdqvygiw-build-bootstrap-guile.sh" "/gnu/store/mzfkrxd4w8vqrmyrx169wj8wyw7r8i37-bash") "i686-linux" "/gnu/store/mzfkrxd4w8 […]
>
> So this process is busy comparing deep structures, probably as a
> consequence of 5cf4b26d52bcea382d98fb4becce89be9ee37b55.

With some debugging, I found that the pathological behavior comes from
the memoization hash table of ‘derivation->bytevector’, specifically
after ‘invalidate-derivation-caches!’ has been called.

Namely, after ‘invalidate-derivation-caches!’ has been called, that hash
table has 24K buckets, including 72 buckets of size 6 or more.  One
bucket has 18 entries, which are all alike:

  #<derivation #f => /gnu/store/…-module-import-compiled 94283c0>

The ‘equal?’ calls come from those buckets, and each of them involves
traversing the whole <derivation> tree.

I’m looking for a workaround.

Ludo’.

PS: Below is some debugging code.