Improve addrman Select() performance when buckets are nearly empty #6530

pull sipa wants to merge 1 commits into bitcoin:master from sipa:fastselect changing 1 files +8 −4

sipa commented at 5:49 PM on August 6, 2015: member

Earlier, when there are only a few entries in the addrman tables, Select() could spin for long periods of time (~200ms), resulting in high CPU usage (up to 40% here). This reduces it to around 0.3ms (0.5% CPU).
sipa force-pushed on Aug 6, 2015
sipa force-pushed on Aug 6, 2015
dgenr8 commented at 3:38 AM on August 7, 2015: contributor

utACK
laanwj added the label P2P on Aug 7, 2015
TheBlueMatt commented at 1:37 PM on August 8, 2015: member

utACK
gmaxwell commented at 10:05 PM on August 22, 2015: contributor

ACK
Improve addrman Select() performance when buckets are nearly empty c33c11ebac

in src/addrman.cpp:None in 9ddf0fdce3 outdated

 340 | @@ -341,8 +341,11 @@ CAddrInfo CAddrMan::Select_()
 341 |          while (1) {
 342 |              int nKBucket = GetRandInt(ADDRMAN_TRIED_BUCKET_COUNT);
 343 |              int nKBucketPos = GetRandInt(ADDRMAN_BUCKET_SIZE);
 344 | -            if (vvTried[nKBucket][nKBucketPos] == -1)
 345 | -                continue;
 346 | +            while (1) {

laanwj commented at 12:05 PM on August 24, 2015:

Equivalent but maybe slightly more readable:

while(vvTried[nKBucket][nKBucketPos] == -1) {
    nKBucket = (nKBucket + insecure_rand()) % ADDRMAN_TRIED_BUCKET_COUNT;
    nKBucketPos = (nKBucketPos + insecure_rand()) % ADDRMAN_BUCKET_SIZE;
}

sipa commented at 12:01 AM on August 26, 2015:

Nit addressed.

sipa force-pushed on Aug 26, 2015
dcousens commented at 2:07 AM on August 26, 2015: contributor

utACK
laanwj merged this on Aug 26, 2015
laanwj closed this on Aug 26, 2015
laanwj referenced this in commit ea19c2bc3f on Aug 26, 2015
DrahtBot locked this on Sep 8, 2021

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