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gossmap: reduce load times by 20%

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It's actually quite quick to load a cache-hot 308,874,377 byte
gossip_store (normal -Og build), but perf does show time spent
in siphash(), which is a bit overkill here, so drop that:

Before:
	Time to load: 66718983-78037766(7.00553e+07+/-2.8e+06)nsec
	
After: 
	Time to load: 54510433-57991725(5.61457e+07+/-1e+06)nsec

We could save maybe 10% more by disabling checksums, but having
that assurance is nice.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2026-02-12 09:12:10 +10:30
parent 120c9d8ce4
commit 5e1bbb08c7
1 changed files with 9 additions and 6 deletions
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15
common/gossmap.c
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@@ -29,11 +29,7 @@ static bool chanidx_eq_id(const ptrint_t *pidx,
struct short_channel_id pidxid = chanidx_id(pidx);
return short_channel_id_eq(pidxid, scid);
}
static size_t scid_hash(const struct short_channel_id scid)
{
return siphash24(siphash_seed(), &scid, sizeof(scid));
}
HTABLE_DEFINE_NODUPS_TYPE(ptrint_t, chanidx_id, scid_hash, chanidx_eq_id,
HTABLE_DEFINE_NODUPS_TYPE(ptrint_t, chanidx_id, short_channel_id_hash, chanidx_eq_id,
chanidx_htable);
static struct node_id nodeidx_id(const ptrint_t *pidx);
@@ -42,9 +38,16 @@ static bool nodeidx_eq_id(const ptrint_t *pidx, const struct node_id id)
struct node_id pidxid = nodeidx_id(pidx);
return node_id_eq(&pidxid, &id);
}
/* You need to spend sats to create a channel to advertize your nodeid,
* so creating clashes is not free: we can be lazy! */
static size_t nodeid_hash(const struct node_id id)
{
return siphash24(siphash_seed(), &id, PUBKEY_CMPR_LEN);
size_t val;
size_t off = siphash_seed()->u.u8[0] % 16;
BUILD_ASSERT(15 + sizeof(val) < sizeof(id.k));
memcpy(&val, id.k + off, sizeof(val));
return val;
}
HTABLE_DEFINE_NODUPS_TYPE(ptrint_t, nodeidx_id, nodeid_hash, nodeidx_eq_id,
nodeidx_htable);