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ruby: Fix the way stall map size is checked for availability

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To ensure that enqueuer observes the practical availability. We
check the message buffer queue size at the start of the cycle.
We also add the size of the stall queue to consider the total
queue size. However, messages can be moved from regular queue
to stall map. This leads to messages being considered twice leading
to false flow control. This patch fixes it by storing the stall map
size at the beginning of the cycle and considering it for checking
availability.

Change-Id: I6ea94f34fe5279b91f74e106d43263e55ec4bf06
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20389
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
This commit is contained in:
Srikant Bharadwaj
2019-08-26 16:41:04 -04:00
parent 5cc0db697d
commit c67c11b60f
2 changed files with 13 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
src/mem/ruby/network/MessageBuffer.cc
View File

@@ -51,6 +51,7 @@ MessageBuffer::MessageBuffer(const Params *p)
m_consumer = NULL;
m_size_last_time_size_checked = 0;
m_size_at_cycle_start = 0;
m_stalled_at_cycle_start = 0;
m_msgs_this_cycle = 0;
m_priority_rank = 0;
@@ -89,10 +90,12 @@ MessageBuffer::areNSlotsAvailable(unsigned int n, Tick current_time)
// until schd cycle, but enqueue operations effect the visible
// size immediately
unsigned int current_size = 0;
unsigned int current_stall_size = 0;
if (m_time_last_time_pop < current_time) {
// no pops this cycle - heap size is correct
// no pops this cycle - heap and stall queue size is correct
current_size = m_prio_heap.size();
current_stall_size = m_stall_map_size;
} else {
if (m_time_last_time_enqueue < current_time) {
// no enqueues this cycle - m_size_at_cycle_start is correct
@@ -102,15 +105,19 @@ MessageBuffer::areNSlotsAvailable(unsigned int n, Tick current_time)
// enqueued msgs to m_size_at_cycle_start
current_size = m_size_at_cycle_start + m_msgs_this_cycle;
}
// Stall queue size at start is considered
current_stall_size = m_stalled_at_cycle_start;
}
// now compare the new size with our max size
if (current_size + m_stall_map_size + n <= m_max_size) {
if (current_size + current_stall_size + n <= m_max_size) {
return true;
} else {
DPRINTF(RubyQueue, "n: %d, current_size: %d, heap size: %d, "
"m_max_size: %d\n",
n, current_size, m_prio_heap.size(), m_max_size);
n, current_size + current_stall_size,
m_prio_heap.size(), m_max_size);
m_not_avail_count++;
return false;
}
@@ -234,6 +241,7 @@ MessageBuffer::dequeue(Tick current_time, bool decrement_messages)
// adjusted until schd cycle
if (m_time_last_time_pop < current_time) {
m_size_at_cycle_start = m_prio_heap.size();
m_stalled_at_cycle_start = m_stall_map_size;
m_time_last_time_pop = current_time;
}
@@ -274,6 +282,7 @@ MessageBuffer::clear()
m_time_last_time_enqueue = 0;
m_time_last_time_pop = 0;
m_size_at_cycle_start = 0;
m_stalled_at_cycle_start = 0;
m_msgs_this_cycle = 0;
}

1
src/mem/ruby/network/MessageBuffer.hh
View File

@@ -192,6 +192,7 @@ class MessageBuffer : public SimObject
Tick m_last_arrival_time;
unsigned int m_size_at_cycle_start;
unsigned int m_stalled_at_cycle_start;
unsigned int m_msgs_this_cycle;
Stats::Scalar m_not_avail_count; // count the # of times I didn't have N