From: Ryujiro Shibuya <ryujiro.shibuya@owmobility.com>
Date: Wed, 16 Oct 2019 05:30:02 +0000 (+0100)
Subject: svm: immediate fifo growth even when wrapped
X-Git-Tag: v20.05-rc0~616
X-Git-Url: https://gerrit.fd.io/r/gitweb?p=vpp.git;a=commitdiff_plain;h=8e20fe7ab445e2de80caabb298aef8a658f6d4ab

svm: immediate fifo growth even when wrapped

Type: fix

- when the fifo is wrapped, and if applicable, insert a new chunk after
  the tail-chunk and rebuild the rb_tree.
- make sure that this new algorithm can be applied only when the fifo is
  used by a single thread (master-thread of the fifo).

Signed-off-by: Ryujiro Shibuya <ryujiro.shibuya@owmobility.com>
Change-Id: I3fc187bc496ea537ca24381e4abc08d2906c9e03
---

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index 6bd6f9157bc..975a82026f7 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -590,6 +590,95 @@ svm_fifo_add_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c)
       f->flags |= SVM_FIFO_F_MULTI_CHUNK;
     }
 
+  /* If fifo is not wrapped, update the size now */
+  if (!svm_fifo_is_wrapped (f))
+    {
+      /* Initialize chunks and add to lookup rbtree */
+      cur = c;
+      if (f->new_chunks)
+	{
+	  prev = f->new_chunks;
+	  while (prev->next)
+	    prev = prev->next;
+	  prev->next = c;
+	}
+      else
+	prev = f->end_chunk;
+
+      while (cur)
+	{
+	  cur->start_byte = prev->start_byte + prev->length;
+	  rb_tree_add2 (&f->chunk_lookup, cur->start_byte,
+			pointer_to_uword (cur));
+	  prev = cur;
+	  cur = cur->next;
+	}
+
+      ASSERT (!f->new_chunks);
+      svm_fifo_grow (f, c);
+      return;
+    }
+
+  /* Wrapped */
+  if (f->flags & SVM_FIFO_F_SINGLE_THREAD_OWNED)
+    {
+      ASSERT (f->master_thread_index == os_get_thread_index ());
+
+      if (!f->new_chunks && f->head_chunk != f->tail_chunk)
+	{
+	  u32 head = 0, tail = 0;
+	  f_load_head_tail_cons (f, &head, &tail);
+
+	  svm_fifo_chunk_t *tmp = f->tail_chunk->next;
+
+	  prev = f->tail_chunk;
+	  u32 add_bytes = 0;
+	  cur = prev->next;
+	  while (cur != f->start_chunk)
+	    {
+	      /* remove any existing rb_tree entry */
+	      rb_tree_del (&f->chunk_lookup, cur->start_byte);
+	      cur = cur->next;
+	    }
+
+	  /* insert new chunk after the tail_chunk */
+	  f->tail_chunk->next = c;
+	  while (c)
+	    {
+	      add_bytes += c->length;
+	      c->start_byte = prev->start_byte + prev->length;
+	      rb_tree_add2 (&f->chunk_lookup, c->start_byte,
+			    pointer_to_uword (c));
+
+	      prev = c;
+	      c = c->next;
+	    }
+	  prev->next = tmp;
+
+	  /* shift existing chunks along */
+	  cur = tmp;
+	  while (cur != f->start_chunk)
+	    {
+	      cur->start_byte = prev->start_byte + prev->length;
+	      rb_tree_add2 (&f->chunk_lookup, cur->start_byte,
+			    pointer_to_uword (cur));
+	      prev = cur;
+	      cur = cur->next;
+	    }
+
+	  f->size += add_bytes;
+	  f->nitems = f->size - 1;
+	  f->new_chunks = 0;
+	  head += add_bytes;
+
+	  clib_atomic_store_rel_n (&f->head, head);
+	  ASSERT (svm_fifo_is_sane (f));
+
+	  return;
+	}
+    }
+
+  /* Wrapped, and optimization of single-thread-owned fifo cannot be applied */
   /* Initialize chunks and add to lookup rbtree */
   cur = c;
   if (f->new_chunks)
@@ -611,14 +700,6 @@ svm_fifo_add_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c)
       cur = cur->next;
     }
 
-  /* If fifo is not wrapped, update the size now */
-  if (!svm_fifo_is_wrapped (f))
-    {
-      ASSERT (!f->new_chunks);
-      svm_fifo_grow (f, c);
-      return;
-    }
-
   /* Postpone size update */
   if (!f->new_chunks)
     {
@@ -1152,6 +1233,25 @@ svm_fifo_is_sane (svm_fifo_t * f)
   return 1;
 }
 
+u8
+svm_fifo_set_single_thread_owned (svm_fifo_t * f)
+{
+  if (f->flags & SVM_FIFO_F_SINGLE_THREAD_OWNED)
+    {
+      if (f->master_thread_index == os_get_thread_index ())
+	{
+	  /* just a duplicate call */
+	  return 0;
+	}
+
+      /* already owned by another thread */
+      return 1;
+    }
+
+  f->flags |= SVM_FIFO_F_SINGLE_THREAD_OWNED;
+  return 0;
+}
+
 u8 *
 format_ooo_segment (u8 * s, va_list * args)
 {
diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index 64ed53bf827..ce4c53d9abe 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -70,6 +70,7 @@ typedef enum svm_fifo_flag_
   SVM_FIFO_F_SHRINK = 1 << 2,
   SVM_FIFO_F_COLLECT_CHUNKS = 1 << 3,
   SVM_FIFO_F_LL_TRACKED = 1 << 4,
+  SVM_FIFO_F_SINGLE_THREAD_OWNED = 1 << 5,
 } svm_fifo_flag_t;
 
 typedef struct _svm_fifo
@@ -477,6 +478,14 @@ ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);
  * @return 	1 if sane, 0 otherwise
  */
 u8 svm_fifo_is_sane (svm_fifo_t * f);
+/**
+ * Declare this fifo is used by only a single thread.
+ * In this special case, fifo-growth can be done in an efficient way without delay.
+ *
+ * @param f             fifo
+ * @return              1 if the fifo is already owned by another thread, 0 otherwise
+ */
+u8 svm_fifo_set_single_thread_owned (svm_fifo_t * f);
 format_function_t format_svm_fifo;
 
 /**