Bug#380509: Estimating the size of the DynamicMMap from the size of the package files
Hi,
Attached is an experimental patch to estimate the size of the
DynamicMMap from the size of the Release files that the cache is
generated from, instead of using a hardcoded estimate of 24MB.
I discarded my test builds (and accidentally the notes) about it
when I expected DynamicMMap to be removed entirely. IIRC, the
estimate is about double the size of the final cache; it should be
the size of the uncompressed Packages files (23MB for Lenny, 25MB
for Sid).
Patch is for apt-0.7.18
Steve
Sat Nov 29 12:23:08 GMT 2008 Steve Cotton <steve@s.cotton.clara.co.uk>
* 380509: set the size of the DynamicMMap based on the size of the package files
This changes pkgMakeStatusCache, but not pkgMakeOnlyStatusCache.
The latter is appears to only be called from debDpkgDB::ReadyPkgCache, which
itself is exported, but only called in two test files scratch.cc and
testextract.cc (searched Apt and Aptitude for others).
diff -rN -u old-apt-0.7.18.steve.2/apt-pkg/pkgcachegen.cc new-apt-0.7.18.steve.2/apt-pkg/pkgcachegen.cc
--- old-apt-0.7.18.steve.2/apt-pkg/pkgcachegen.cc 2008-11-29 12:40:25.000000000 +0000
+++ new-apt-0.7.18.steve.2/apt-pkg/pkgcachegen.cc 2008-11-29 12:40:25.000000000 +0000
@@ -793,8 +793,6 @@
bool pkgMakeStatusCache(pkgSourceList &List,OpProgress &Progress,
MMap **OutMap,bool AllowMem)
{
- unsigned long MapSize = _config->FindI("APT::Cache-Limit",24*1024*1024);
-
vector<pkgIndexFile *> Files;
for (vector<metaIndex *>::const_iterator i = List.begin();
i != List.end();
@@ -836,7 +834,10 @@
}
/* At this point we know we need to reconstruct the package cache,
- begin. */
+ begin by allocating an mmap'd file as large as the total of the
+ input files; all unused space will be truncated afterwards. */
+ unsigned long DefaultMapSize = ComputeSize(Files.begin(),Files.end());
+ unsigned long MapSize = _config->FindI("APT::Cache-Limit", DefaultMapSize);
SPtr<FileFd> CacheF;
SPtr<DynamicMMap> Map;
if (Writeable == true && CacheFile.empty() == false)
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