From e8a7b0b28ca01cd8c2c1bee0d83e5997b40de689 Mon Sep 17 00:00:00 2001 From: David Kalnischkies Date: Wed, 11 Jun 2014 20:42:16 +0200 Subject: increase hashtable size for packages/groups by factor 5 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It also makes the size configureable, so it can be adapted in the future without the need for an abi break - and even by users… The increase was long overdue as it gives a >10% decrease in runtime of e.g. 'apt-get check -s'. Some (useless) benchmark with 69933 groups and 187796 packages without a pre-built cache: time apt-get check -so APT::Cache-HashTableSize=1 → 20m time apt-get check -so APT::Cache-HashTableSize=1000 → 6,41s time apt-get check -so APT::Cache-HashTableSize=2000 → 5,64s (old) time apt-get check -so APT::Cache-HashTableSize=3000 → 5,30s time apt-get check -so APT::Cache-HashTableSize=5000 → 5,08s time apt-get check -so APT::Cache-HashTableSize=6000 → 5,05s time apt-get check -so APT::Cache-HashTableSize=7000 → 5,02s time apt-get check -so APT::Cache-HashTableSize=8000 → 5,00s time apt-get check -so APT::Cache-HashTableSize=9000 → 4,98s time apt-get check -so APT::Cache-HashTableSize=10000 → 4,96s (new) time apt-get check -so APT::Cache-HashTableSize=15000 → 4,90s time apt-get check -so APT::Cache-HashTableSize=20000 → 4,86s time apt-get check -so APT::Cache-HashTableSize=30000 → 4,77s time apt-get check -so APT::Cache-HashTableSize=40000 → 4,74s time apt-get check -so APT::Cache-HashTableSize=50000 → 4,73s time apt-get check -so APT::Cache-HashTableSize=60000 → 4,71s The gap increases further for operations which have more package lookups. Factor 5 was chosen as higher values do not provide any really significant timing advantage anymore compared to the memory increase in my testing and there is always the possibility to increase it now if that changes. (also most users will not have 3 releases and 4 architectures in the cache, so theirs will be much smaller and faster). --- apt-pkg/pkgcache.cc | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) (limited to 'apt-pkg/pkgcache.cc') diff --git a/apt-pkg/pkgcache.cc b/apt-pkg/pkgcache.cc index 4fbdc93d5..7b092f07e 100644 --- a/apt-pkg/pkgcache.cc +++ b/apt-pkg/pkgcache.cc @@ -54,8 +54,8 @@ pkgCache::Header::Header() /* Whenever the structures change the major version should be bumped, whenever the generator changes the minor version should be bumped. */ - MajorVersion = 9; - MinorVersion = 2; + MajorVersion = 10; + MinorVersion = 0; Dirty = false; HeaderSz = sizeof(pkgCache::Header); @@ -85,8 +85,7 @@ pkgCache::Header::Header() StringList = 0; VerSysName = 0; Architecture = 0; - memset(PkgHashTable,0,sizeof(PkgHashTable)); - memset(GrpHashTable,0,sizeof(GrpHashTable)); + HashTableSize = _config->FindI("APT::Cache-HashTableSize", 10 * 1048); memset(Pools,0,sizeof(Pools)); CacheFileSize = 0; @@ -194,7 +193,7 @@ unsigned long pkgCache::sHash(const string &Str) const unsigned long Hash = 0; for (string::const_iterator I = Str.begin(); I != Str.end(); ++I) Hash = 41 * Hash + tolower_ascii(*I); - return Hash % _count(HeaderP->PkgHashTable); + return Hash % HeaderP->HashTableSize; } unsigned long pkgCache::sHash(const char *Str) const @@ -202,7 +201,7 @@ unsigned long pkgCache::sHash(const char *Str) const unsigned long Hash = tolower_ascii(*Str); for (const char *I = Str + 1; *I != 0; ++I) Hash = 41 * Hash + tolower_ascii(*I); - return Hash % _count(HeaderP->PkgHashTable); + return Hash % HeaderP->HashTableSize; } /*}}}*/ // Cache::SingleArchFindPkg - Locate a package by name /*{{{*/ @@ -213,7 +212,7 @@ unsigned long pkgCache::sHash(const char *Str) const pkgCache::PkgIterator pkgCache::SingleArchFindPkg(const string &Name) { // Look at the hash bucket - Package *Pkg = PkgP + HeaderP->PkgHashTable[Hash(Name)]; + Package *Pkg = PkgP + HeaderP->PkgHashTable()[Hash(Name)]; for (; Pkg != PkgP; Pkg = PkgP + Pkg->Next) { if (unlikely(Pkg->Name == 0)) @@ -278,7 +277,7 @@ pkgCache::GrpIterator pkgCache::FindGrp(const string &Name) { return GrpIterator(*this,0); // Look at the hash bucket for the group - Group *Grp = GrpP + HeaderP->GrpHashTable[sHash(Name)]; + Group *Grp = GrpP + HeaderP->GrpHashTable()[sHash(Name)]; for (; Grp != GrpP; Grp = GrpP + Grp->Next) { if (unlikely(Grp->Name == 0)) continue; @@ -432,10 +431,10 @@ void pkgCache::GrpIterator::operator ++(int) S = Owner->GrpP + S->Next; // Follow the hash table - while (S == Owner->GrpP && (HashIndex+1) < (signed)_count(Owner->HeaderP->GrpHashTable)) + while (S == Owner->GrpP && (HashIndex+1) < (signed)Owner->HeaderP->HashTableSize) { HashIndex++; - S = Owner->GrpP + Owner->HeaderP->GrpHashTable[HashIndex]; + S = Owner->GrpP + Owner->HeaderP->GrpHashTable()[HashIndex]; } } /*}}}*/ @@ -449,10 +448,10 @@ void pkgCache::PkgIterator::operator ++(int) S = Owner->PkgP + S->Next; // Follow the hash table - while (S == Owner->PkgP && (HashIndex+1) < (signed)_count(Owner->HeaderP->PkgHashTable)) + while (S == Owner->PkgP && (HashIndex+1) < (signed)Owner->HeaderP->HashTableSize) { HashIndex++; - S = Owner->PkgP + Owner->HeaderP->PkgHashTable[HashIndex]; + S = Owner->PkgP + Owner->HeaderP->PkgHashTable()[HashIndex]; } } /*}}}*/ -- cgit v1.2.3