This patch adds a new TM method, ml_wt, which uses an array of locks
with version numbers and runs a write-through algorithm with time-based
validations and snapshot time extensions.
patch1 adds xcalloc as a helper function for allocations (used in the
new TM method).
patch2 improves TM method reinitialization (helps ml_wt avoid
reallocation of the lock array) and adds a hook to TM methods so that
they can report back whether they can deal with the current runtime
situation (e.g., a the current number of threads).
patch3 is the actual TM method.
Tested on ppc64 with up to 64 threads with both microbenchmarks and
STAMP. OK for trunk?
commit c0d1d1778b18f3dfc4a136e5a807c2fecbeb64e4
Author: Torvald Riegel trie...@redhat.com
Date: Thu Feb 9 13:44:38 2012 +0100
libitm: Add xcalloc.
libitm/
* util.cc (GTM::xcalloc): New.
* common.h (GTM::xcalloc): Declare.
diff --git a/libitm/common.h b/libitm/common.h
index 14d0efb..b1ef2d4 100644
--- a/libitm/common.h
+++ b/libitm/common.h
@@ -54,6 +54,8 @@ namespace GTM HIDDEN {
// cache lines that are not shared with any object used by another thread.
extern void * xmalloc (size_t s, bool separate_cl = false)
__attribute__((malloc, nothrow));
+extern void * xcalloc (size_t s, bool separate_cl = false)
+ __attribute__((malloc, nothrow));
extern void * xrealloc (void *p, size_t s, bool separate_cl = false)
__attribute__((malloc, nothrow));
diff --git a/libitm/util.cc b/libitm/util.cc
index afd37e4..48a1bf8 100644
--- a/libitm/util.cc
+++ b/libitm/util.cc
@@ -71,6 +71,18 @@ xmalloc (size_t size, bool separate_cl)
}
void *
+xcalloc (size_t size, bool separate_cl)
+{
+ // TODO Use posix_memalign if separate_cl is true, or some other allocation
+ // method that will avoid sharing cache lines with data used by other
+ // threads.
+ void *r = calloc (1, size);
+ if (r == 0)
+GTM_fatal (Out of memory allocating %lu bytes, (unsigned long) size);
+ return r;
+}
+
+void *
xrealloc (void *old, size_t size, bool separate_cl)
{
// TODO Use posix_memalign if separate_cl is true, or some other allocation
commit 3b486db323b51ea87e1f64cd3abb9402f7c7307a
Author: Torvald Riegel trie...@redhat.com
Date: Thu Feb 9 13:50:10 2012 +0100
libitm: Improve method reinit and choice.
libitm/
* dispatch.h (GTM::abi_dispatch::supports): New.
(GTM::method_group::reinit): New.
* retry.cc (GTM::gtm_thread::decide_retry_strategy): Use reinit().
(GTM::gtm_thread::number_of_threads_changed): Check that the method
supports the current situation.
diff --git a/libitm/dispatch.h b/libitm/dispatch.h
index dbf05e4..d059c49 100644
--- a/libitm/dispatch.h
+++ b/libitm/dispatch.h
@@ -245,6 +245,12 @@ struct method_group
// Stop using any method from this group for now. This can be used to
// destruct meta data as soon as this method group is not used anymore.
virtual void fini() = 0;
+ // This can be overriden to implement more light-weight re-initialization.
+ virtual void reinit()
+ {
+fini();
+init();
+ }
};
@@ -290,6 +296,10 @@ public:
// method on begin of a nested transaction without committing or restarting
// the parent method.
virtual abi_dispatch* closed_nesting_alternative() { return 0; }
+ // Returns true iff this method group supports the current situation.
+ // NUMBER_OF_THREADS is the current number of threads that might execute
+ // transactions.
+ virtual bool supports(unsigned number_of_threads) { return true; }
bool read_only () const { return m_read_only; }
bool write_through() const { return m_write_through; }
diff --git a/libitm/retry.cc b/libitm/retry.cc
index decd773..6e05f5f 100644
--- a/libitm/retry.cc
+++ b/libitm/retry.cc
@@ -58,11 +58,8 @@ GTM::gtm_thread::decide_retry_strategy (gtm_restart_reason r)
serial_lock.read_unlock(this);
serial_lock.write_lock();
if (disp-get_method_group() == default_dispatch-get_method_group())
- {
- // Still the same method group.
- disp-get_method_group()-fini();
- disp-get_method_group()-init();
- }
+ // Still the same method group.
+ disp-get_method_group()-reinit();
serial_lock.write_unlock();
serial_lock.read_lock(this);
if (disp-get_method_group() != default_dispatch-get_method_group())
@@ -72,11 +69,8 @@ GTM::gtm_thread::decide_retry_strategy (gtm_restart_reason r)
}
}
else
- {
- // We are a serial transaction already, which makes things simple.
- disp-get_method_group()-fini();
- disp-get_method_group()-init();
- }
+ // We are a serial transaction already, which makes things simple.
+ disp-get_method_group()-reinit();
}
bool retry_irr = (r == RESTART_SERIAL_IRR);
@@ -249,7 +243,7 @@ GTM::gtm_thread::number_of_threads_changed(unsigned
previous, unsigned now)
