urbit/shrub
1
1
Fork 0
mirror of https://github.com/urbit/shrub.git synced 2024-12-23 19:05:48 +03:00
Code Issues Packages Projects Releases Wiki Activity

noun: don't add identical values to song_x_cape's hashtable

Browse Source 
We were unconditionally adding equal items to the hashtable of
already-compared pointers.  This table exists so that if we've already
determined two non-pointer-equal nouns are value-equal, we don't have to
check them again.  However, atoms (especially direct) ended up in this
hashtable even though we don't look those up.  This makes sure we don't
add items to the hashtable if they're "pointer"-equal (which for direct
atoms is value-equal).

The impact of this inefficiency was greatly magnified by the issue with
+mug where (mug a a) = (mug b b) for all a, b.  For this reason, these
identical pairs added to the hashtable always had the same mug, so they
were added to the same bucket, which meant adding to that list required
linearly traversing the entire bucket.

This was the first barrier that was causing |pack to take a long time on
ships which distribute OTAs, but it isn't a complete solution for |pack.
This commit is contained in:
Philip Monk 2020-07-15 12:33:54 -07:00
parent 462a3429ef
commit 7ded3f127c
No known key found for this signature in database
GPG Key ID: B66E1F02604E44EC
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
pkg/urbit/noun/retrieve.c
View File

@ -373,11 +373,13 @@ _song_x_cape(c3_ys mov, c3_ys off,
// we cons [a] and [b] as posts so that we don't
// touch their reference counts.
//
key = u3nc(u3a_to_off(a), u3a_to_off(b));
u3t_off(euq_o);
u3h_put(har_p, key, c3y);
u3t_on(euq_o);
u3z(key);
if ( a != b ) {
key = u3nc(u3a_to_off(a), u3a_to_off(b));
u3t_off(euq_o);
u3h_put(har_p, key, c3y);
u3t_on(euq_o);
u3z(key);
}
fam = _eq_pop(mov, off);
}