From ec035930754cd19244486963581ed4f04459d4c8 Mon Sep 17 00:00:00 2001
From: Philippe Canal <pcanal@fnal.gov>
Date: Thu, 11 Feb 2021 16:22:20 -0600
Subject: [PATCH] TBufferMergerFile: Call FlushBasket in unlocked thread.
Add new enum for TObject::Write: kOnlyPrepStep = BIT(3) ///< Just prepare the objects do not write them (i.e. call TTree::FlushBaskets)
---
core/base/inc/TObject.h | 11 ++++++++++-
core/base/src/TObject.cxx | 3 +++
io/io/src/TBufferMergerFile.cxx | 4 ++++
io/io/src/TDirectoryFile.cxx | 3 ++-
tree/tree/src/TTree.cxx | 2 ++
5 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/core/base/inc/TObject.h b/core/base/inc/TObject.h
index 58c09609f69..f3646aa4f4c 100644
--- a/core/base/inc/TObject.h
+++ b/core/base/inc/TObject.h
@@ -86,7 +86,16 @@ public:
enum {
kSingleKey = BIT(0), ///< write collection with single key
kOverwrite = BIT(1), ///< overwrite existing object with same name
- kWriteDelete = BIT(2) ///< write object, then delete previous key with same name
+ kWriteDelete = BIT(2), ///< write object, then delete previous key with same name
+
+ ///< Used to request that the class specific implementation of `TObject::Write`
+ ///< just prepare the objects to be ready to be written but do not actually write
+ ///< them into the TBuffer. This is just for example by TBufferMerger to request
+ ///< that the TTree inside the file calls `TTree::FlushBaskets` (outside of the merging lock)
+ ///< and TBufferMerger will later ask for the write (inside the merging lock).
+ ///< To take advantage of this feature the class needs to overload `TObject::Write`
+ ///< and use this enum value accordingly. (See `TTree::Write` and `TObject::Write`)
+ kOnlyPrepStep = BIT(3)
};
TObject();
diff --git a/core/base/src/TObject.cxx b/core/base/src/TObject.cxx
index 8d5cf8ba115..e9e54301d11 100644
--- a/core/base/src/TObject.cxx
+++ b/core/base/src/TObject.cxx
@@ -771,6 +771,9 @@ void TObject::UseCurrentStyle()
Int_t TObject::Write(const char *name, Int_t option, Int_t bufsize) const
{
+ if (R__unlikely(option & kOnlyPrepStep))
+ return 0;
+
TString opt = "";
if (option & kSingleKey) opt += "SingleKey";
if (option & kOverwrite) opt += "OverWrite";
diff --git a/io/io/src/TBufferMergerFile.cxx b/io/io/src/TBufferMergerFile.cxx
index 249882bfc67..634fa8a5064 100644
--- a/io/io/src/TBufferMergerFile.cxx
+++ b/io/io/src/TBufferMergerFile.cxx
@@ -29,6 +29,10 @@ TBufferMergerFile::~TBufferMergerFile()
Int_t TBufferMergerFile::Write(const char *name, Int_t opt, Int_t bufsize)
{
+ // Make sure the compression of the basket is done in the unlocked thread and
+ // not in the locked section.
+ TMemFile::Write(name, opt | TObject::kOnlyPrepStep, bufsize);
+
// Instead of Writing the TTree, doing a memcpy, Pushing to the queue
// then Reading and then deleting, let's see if we can just merge using
// the live TTree.
diff --git a/io/io/src/TDirectoryFile.cxx b/io/io/src/TDirectoryFile.cxx
index 15ae3e635c1..b4dc18fff3e 100644
--- a/io/io/src/TDirectoryFile.cxx
+++ b/io/io/src/TDirectoryFile.cxx
@@ -1785,7 +1785,8 @@ Int_t TDirectoryFile::Write(const char *, Int_t opt, Int_t bufsize)
while ((obj=next())) {
nbytes += obj->Write(0,opt,bufsize);
}
- SaveSelf(kTRUE); // force save itself
+ if (R__likely(!(opt & kOnlyPrepStep)))
+ SaveSelf(kTRUE); // force save itself
return nbytes;
}
diff --git a/tree/tree/src/TTree.cxx b/tree/tree/src/TTree.cxx
index 31240e96517..99837711e20 100644
--- a/tree/tree/src/TTree.cxx
+++ b/tree/tree/src/TTree.cxx
@@ -9576,6 +9576,8 @@ void TTree::UseCurrentStyle()
Int_t TTree::Write(const char *name, Int_t option, Int_t bufsize) const
{
FlushBasketsImpl();
+ if (R__unlikely(option & kOnlyPrepStep))
+ return 0;
return TObject::Write(name, option, bufsize);
}
--
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