jplevyak commented on code in PR #13893:
URL: https://github.com/apache/trafficserver/pull/13893#discussion_r4366037348
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src/iocore/cache/RamCacheCLFUS.cc:
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@@ -943,7 +977,7 @@ RamCacheCLFUS::put(CryptoHash *key, IOBufferData *data,
uint32_t len, bool copy,
e = THREAD_ALLOC(ramCacheCLFUSEntryAllocator, this_ethread());
e->key = *key;
e->auxkey = auxkey;
- e->hits = 1;
+ e->hits = 2;
e->size = data->block_size();
e->flags = 0;
this->_bucket[i].push(e);
Review Comment:
The hits = 2 line only runs for history entries; it isn't shared with
resident entries:
- Lhistory: (RamCacheCLFUS.cc ~line 991). This is the only place set to
hits = 2. It always creates a history entry: it sets flag_bits.lru = 1, queues
the entry on _lru[1] and increments _history.
- Linsert: (~line 959). New resident entries are created here, and they
still start at hits = 1. The PR doesn't change this line.
Copilot does have half a point. A history entry that is later admitted
keeps its hits count. So an object that went through history becomes resident
with a higher count than one admitted directly. That is deliberate: it was
requested again while in history, so it has earned the extra weight. The hits =
2 start also gives it more than one _tick() before it ages out of history. That
retention is what the PR description means by "a multi-tick chance".
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