Perf-sc: tdf#100709 Use a "one and a half" alloc strategy for ScMarkArray

ScMarkArray::SetMarkArea()
before, Ir:   3 059 572 314
 after, Ir:   1 195 743 815

ScDocShell::Load()
before, Ir:  17 337 645 368
 after, Ir:  15 497 093 406

Change-Id: I83959f0dfcf6480781a44b5cfc36242a5c35ebd4

1 files changed, 10 insertions, 1 deletions

diff --git a/sc/source/core/data/markarr.cxx b/sc/source/core/data/markarr.cxx
index 52b7597fe1cd..248ddd0cb4c0 100644
--- a/sc/source/core/data/markarr.cxx
+++ b/sc/source/core/data/markarr.cxx
@@ -121,7 +121,16 @@ void ScMarkArray::SetMarkArea( SCROW nStartRow, SCROW nEndRow, bool bMarked )
                 SCSIZE nNeeded = nCount + 2;
                 if ( nLimit < nNeeded )
                 {
-                    nLimit += SC_MARKARRAY_DELTA;
+                    // Assume that if it grew already beyond a certain
+                    // threshold it will continue to grow and avoid the
+                    // bottleneck of lots of reallocations in small steps.
+                    // Don't use a simple "double amount" strategy though as
+                    // that again may allocate much more than actually needed.
+                    // The "one and a half" is just a shot into the blue sky.
+                    if (nLimit > 4 * SC_MARKARRAY_DELTA)
+                        nLimit += nLimit / 2;
+                    else
+                        nLimit += SC_MARKARRAY_DELTA;
                     if ( nLimit < nNeeded )
                         nLimit = nNeeded;
                     ScMarkEntry* pNewData = new ScMarkEntry[nLimit];