From 28aa539f7da7b172d0f35ea9a63f3986939477f7 Mon Sep 17 00:00:00 2001 From: Sirshak Das Date: Tue, 5 Feb 2019 01:33:33 -0600 Subject: svm_fifo rework to avoid contention on cursize Problems Addressed: - Contention of cursize by producer and consumer. - Reduce the no of modulo operations. Changes: - Synchronization between producer and consumer changed from cursize to head and tail indexes Implications: reduces the usable size of fifo by 1. - Using weaker memory ordering C++11 atomics to access head and tail based on producer and consumer role. - Head and tail indexes are unsigned 32 bit integers. Additions and subtraction on them are implicit 32 bit Modulo operation. - Adding weaker memory ordering variants of max_enq, max_deq, is_empty and is_full Using them appropriately in all places. Perfomance improvement (iperf3 via Hoststack): iperf3 Server: Marvell ThunderX2(AArch64) - iperf3 Client: Skylake(x86) ~6%(256 rxd/txd) - ~11%(2048 rxd/txd) Change-Id: I1d484e000e437430fdd5a819657d1c6b62443018 Signed-off-by: Sirshak Das Reviewed-by: Honnappa Nagarahalli --- src/svm/svm_fifo_segment.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'src/svm/svm_fifo_segment.c') diff --git a/src/svm/svm_fifo_segment.c b/src/svm/svm_fifo_segment.c index e377160f6d8..94bf6a5e73e 100644 --- a/src/svm/svm_fifo_segment.c +++ b/src/svm/svm_fifo_segment.c @@ -381,7 +381,12 @@ svm_fifo_segment_alloc_fifo (svm_fifo_segment_private_t * fs, fsh->free_fifos[freelist_index] = f->next; /* (re)initialize the fifo, as in svm_fifo_create */ clib_memset (f, 0, sizeof (*f)); - f->nitems = data_size_in_bytes; + f->size = (1 << (max_log2 (data_size_in_bytes))); + /* + * usable size of the fifo set to rounded_data_size - 1 + * to differentiate between free fifo and empty fifo. + */ + f->nitems = f->size - 1; f->ooos_list_head = OOO_SEGMENT_INVALID_INDEX; f->ct_session_index = SVM_FIFO_INVALID_SESSION_INDEX; f->refcnt = 1; -- cgit 1.2.3-korg