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author | Jim Brunner <brunnerj@amazon.com> | 2021-02-20 02:56:30 -0800 |
---|---|---|
committer | GitHub <noreply@github.com> | 2021-02-20 12:56:30 +0200 |
commit | 06966d2a0e6a2087e4f70265e0f03fa8e1d1b94b (patch) | |
tree | 3ffb7ad11006d86b57b0f8ecca30499025b24367 /src/dict.c | |
parent | 46346e9e3a30d0d3c52dd21a2ce93898005c7ad9 (diff) | |
download | redis-06966d2a0e6a2087e4f70265e0f03fa8e1d1b94b.tar.gz |
dict: pause rehash, minor readability refactor (#8515)
The `dict` field `iterators` is misleading and incorrect.
This variable is used for 1 purpose - to pause rehashing.
The current `iterators` field doesn't actually count "iterators".
It counts "safe iterators". But - it doesn't actually count safe iterators
either. For one, it's only incremented once the safe iterator begins to
iterate, not when it's created. It's also incremented in `dictScan` to
prevent rehashing (and commented to make it clear why `iterators` is
being incremented during a scan).
This update renames the field as `pauserehash` and creates 2 helper
macros `dictPauseRehashing(d)` and `dictResumeRehashing(d)`
Diffstat (limited to 'src/dict.c')
-rw-r--r-- | src/dict.c | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/src/dict.c b/src/dict.c index 9ae066f33..4a9f3fb0a 100644 --- a/src/dict.c +++ b/src/dict.c @@ -126,7 +126,7 @@ int _dictInit(dict *d, dictType *type, d->type = type; d->privdata = privDataPtr; d->rehashidx = -1; - d->iterators = 0; + d->pauserehash = 0; return DICT_OK; } @@ -264,7 +264,7 @@ long long timeInMilliseconds(void) { * than 0, and is smaller than 1 in most cases. The exact upper bound * depends on the running time of dictRehash(d,100).*/ int dictRehashMilliseconds(dict *d, int ms) { - if (d->iterators > 0) return 0; + if (d->pauserehash > 0) return 0; long long start = timeInMilliseconds(); int rehashes = 0; @@ -276,8 +276,8 @@ int dictRehashMilliseconds(dict *d, int ms) { return rehashes; } -/* This function performs just a step of rehashing, and only if there are - * no safe iterators bound to our hash table. When we have iterators in the +/* This function performs just a step of rehashing, and only if hashing has + * not been paused for our hash table. When we have iterators in the * middle of a rehashing we can't mess with the two hash tables otherwise * some element can be missed or duplicated. * @@ -285,7 +285,7 @@ int dictRehashMilliseconds(dict *d, int ms) { * dictionary so that the hash table automatically migrates from H1 to H2 * while it is actively used. */ static void _dictRehashStep(dict *d) { - if (d->iterators == 0) dictRehash(d,1); + if (d->pauserehash == 0) dictRehash(d,1); } /* Add an element to the target hash table */ @@ -593,7 +593,7 @@ dictEntry *dictNext(dictIterator *iter) dictht *ht = &iter->d->ht[iter->table]; if (iter->index == -1 && iter->table == 0) { if (iter->safe) - iter->d->iterators++; + dictPauseRehashing(iter->d); else iter->fingerprint = dictFingerprint(iter->d); } @@ -625,7 +625,7 @@ void dictReleaseIterator(dictIterator *iter) { if (!(iter->index == -1 && iter->table == 0)) { if (iter->safe) - iter->d->iterators--; + dictResumeRehashing(iter->d); else assert(iter->fingerprint == dictFingerprint(iter->d)); } @@ -896,9 +896,8 @@ unsigned long dictScan(dict *d, if (dictSize(d) == 0) return 0; - /* Having a safe iterator means no rehashing can happen, see _dictRehashStep. - * This is needed in case the scan callback tries to do dictFind or alike. */ - d->iterators++; + /* This is needed in case the scan callback tries to do dictFind or alike. */ + dictPauseRehashing(d); if (!dictIsRehashing(d)) { t0 = &(d->ht[0]); @@ -966,8 +965,7 @@ unsigned long dictScan(dict *d, } while (v & (m0 ^ m1)); } - /* undo the ++ at the top */ - d->iterators--; + dictResumeRehashing(d); return v; } @@ -1056,7 +1054,7 @@ void dictEmpty(dict *d, void(callback)(void*)) { _dictClear(d,&d->ht[0],callback); _dictClear(d,&d->ht[1],callback); d->rehashidx = -1; - d->iterators = 0; + d->pauserehash = 0; } void dictEnableResize(void) { |