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core: prefetch different amount of work items for different queues

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Incoming item processing usually takes more work then completion
item processing. Prefetch more completion items to make sure they are
ready before access.
This commit is contained in:
Gleb Natapov
2015-01-25 17:36:42 +02:00
committed by Avi Kivity
parent 0383459b93
commit 74f9f1fdd2
2 changed files with 7 additions and 7 deletions
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12
core/reactor.cc
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@@ -976,11 +976,11 @@ void smp_message_queue::flush_response_batch() {
_completed_fifo.clear();
}
template<typename Func>
template<size_t PrefetchCnt, typename Func>
size_t smp_message_queue::process_queue(lf_queue& q, Func process) {
// copy batch to local memory in order to minimize
// time in which cross-cpu data is accessed
work_item* items[queue_length + prefetch_cnt];
work_item* items[queue_length + PrefetchCnt];
work_item* wi;
if (!q.pop(wi))
return 0;
@@ -988,10 +988,10 @@ size_t smp_message_queue::process_queue(lf_queue& q, Func process) {
// access with potential cache miss the second pop may cause
prefetch<2>(wi);
auto nr = q.pop(items);
std::fill(std::begin(items) + nr, std::begin(items) + nr + prefetch_cnt, nr ? items[nr - 1] : wi);
std::fill(std::begin(items) + nr, std::begin(items) + nr + PrefetchCnt, nr ? items[nr - 1] : wi);
unsigned i = 0;
do {
prefetch_n<2>(std::begin(items) + i, std::begin(items) + i + prefetch_cnt);
prefetch_n<2>(std::begin(items) + i, std::begin(items) + i + PrefetchCnt);
process(wi);
wi = items[i++];
} while(i <= nr);
@@ -1000,7 +1000,7 @@ size_t smp_message_queue::process_queue(lf_queue& q, Func process) {
}
size_t smp_message_queue::process_completions() {
auto nr = process_queue(_completed, [] (work_item* wi) {
auto nr = process_queue<prefetch_cnt*2>(_completed, [] (work_item* wi) {
wi->complete();
});
_current_queue_length -= nr;
@@ -1015,7 +1015,7 @@ void smp_message_queue::flush_request_batch() {
}
size_t smp_message_queue::process_incoming() {
auto nr = process_queue(_pending, [this] (work_item* wi) {
auto nr = process_queue<prefetch_cnt>(_pending, [this] (work_item* wi) {
wi->process().then([this, wi] {
respond(wi);
});

2
core/reactor.hh
View File

@@ -460,7 +460,7 @@ public:
return fut;
}
void start(unsigned cpuid);
template<typename Func>
template<size_t PrefetchCnt, typename Func>
size_t process_queue(lf_queue& q, Func process);
size_t process_incoming();
size_t process_completions();