X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fsvm%2Ffifo_segment.c;h=48d019c9aace4ffd286ac5a086b38f3211eab839;hb=2711ca710affe0c52bf63e08e0cf0588094e6198;hp=00fb023f3cbad9ddbe38fc44d3848cdc252f67db;hpb=8c517c8fb44e7003ecdb615bc03163536e24d4d4;p=vpp.git

diff --git a/src/svm/fifo_segment.c b/src/svm/fifo_segment.c
index 00fb023f3cb..48d019c9aac 100644
--- a/src/svm/fifo_segment.c
+++ b/src/svm/fifo_segment.c
@@ -105,13 +105,14 @@ fsh_n_active_fifos (fifo_segment_header_t * fsh)
 }
 
 static inline uword
-fsh_virtual_mem (fifo_segment_header_t * fsh)
+fs_virtual_mem (fifo_segment_t *fs)
 {
+  fifo_segment_header_t *fsh = fs->h;
   fifo_segment_slice_t *fss;
   uword total_vm = 0;
   int i;
 
-  for (i = 0; i < fsh->n_slices; i++)
+  for (i = 0; i < fs->n_slices; i++)
     {
       fss = fsh_slice_get (fsh, i);
       total_vm += clib_atomic_load_relax_n (&fss->virtual_mem);
@@ -127,31 +128,22 @@ fsh_virtual_mem_update (fifo_segment_header_t * fsh, u32 slice_index,
   fss->virtual_mem += n_bytes;
 }
 
-static inline void
-fss_chunk_freelist_lock (fifo_segment_slice_t *fss)
+static inline int
+fss_chunk_fl_index_is_valid (fifo_segment_slice_t *fss, u32 fl_index)
 {
-  u32 free = 0;
-  while (!clib_atomic_cmp_and_swap_acq_relax_n (&fss->chunk_lock, &free, 1, 0))
-    {
-      /* atomic load limits number of compare_exchange executions */
-      while (clib_atomic_load_relax_n (&fss->chunk_lock))
-	CLIB_PAUSE ();
-      /* on failure, compare_exchange writes (*p)->lock into free */
-      free = 0;
-    }
+  return (fl_index < FS_CHUNK_VEC_LEN);
 }
 
-static inline void
-fss_chunk_freelist_unlock (fifo_segment_slice_t *fss)
-{
-  /* Make sure all reads/writes are complete before releasing the lock */
-  clib_atomic_release (&fss->chunk_lock);
-}
+#define FS_CL_HEAD_MASK	 0xFFFFFFFFFFFF
+#define FS_CL_HEAD_TMASK 0xFFFF000000000000
+#define FS_CL_HEAD_TINC	 (1ULL << 48)
 
-static inline int
-fss_chunk_fl_index_is_valid (fifo_segment_slice_t * fss, u32 fl_index)
+static svm_fifo_chunk_t *
+fss_chunk_free_list_head (fifo_segment_header_t *fsh,
+			  fifo_segment_slice_t *fss, u32 fl_index)
 {
-  return (fl_index < FS_CHUNK_VEC_LEN);
+  fs_sptr_t headsp = clib_atomic_load_relax_n (&fss->free_chunks[fl_index]);
+  return fs_chunk_ptr (fsh, headsp & FS_CL_HEAD_MASK);
 }
 
 static void
@@ -159,10 +151,20 @@ fss_chunk_free_list_push (fifo_segment_header_t *fsh,
 			  fifo_segment_slice_t *fss, u32 fl_index,
 			  svm_fifo_chunk_t *c)
 {
-  fss_chunk_freelist_lock (fss);
-  c->next = fss->free_chunks[fl_index];
-  fss->free_chunks[fl_index] = fs_chunk_sptr (fsh, c);
-  fss_chunk_freelist_unlock (fss);
+  fs_sptr_t old_head, new_head, csp;
+
+  csp = fs_chunk_sptr (fsh, c);
+  ASSERT (csp <= FS_CL_HEAD_MASK);
+  old_head = clib_atomic_load_acq_n (&fss->free_chunks[fl_index]);
+
+  do
+    {
+      c->next = old_head & FS_CL_HEAD_MASK;
+      new_head = csp + ((old_head + FS_CL_HEAD_TINC) & FS_CL_HEAD_TMASK);
+    }
+  while (!__atomic_compare_exchange (&fss->free_chunks[fl_index], &old_head,
+				     &new_head, 0 /* weak */, __ATOMIC_RELEASE,
+				     __ATOMIC_ACQUIRE));
 }
 
 static void
@@ -170,32 +172,50 @@ fss_chunk_free_list_push_list (fifo_segment_header_t *fsh,
 			       fifo_segment_slice_t *fss, u32 fl_index,
 			       svm_fifo_chunk_t *head, svm_fifo_chunk_t *tail)
 {
-  fss_chunk_freelist_lock (fss);
-  tail->next = fss->free_chunks[fl_index];
-  fss->free_chunks[fl_index] = fs_chunk_sptr (fsh, head);
-  fss_chunk_freelist_unlock (fss);
+  fs_sptr_t old_head, new_head, headsp;
+
+  headsp = fs_chunk_sptr (fsh, head);
+  ASSERT (headsp <= FS_CL_HEAD_MASK);
+  old_head = clib_atomic_load_acq_n (&fss->free_chunks[fl_index]);
+
+  do
+    {
+      tail->next = old_head & FS_CL_HEAD_MASK;
+      new_head = headsp + ((old_head + FS_CL_HEAD_TINC) & FS_CL_HEAD_TMASK);
+    }
+  while (!__atomic_compare_exchange (&fss->free_chunks[fl_index], &old_head,
+				     &new_head, 0 /* weak */, __ATOMIC_RELEASE,
+				     __ATOMIC_ACQUIRE));
 }
 
 static svm_fifo_chunk_t *
 fss_chunk_free_list_pop (fifo_segment_header_t *fsh, fifo_segment_slice_t *fss,
 			 u32 fl_index)
 {
+  fs_sptr_t old_head, new_head;
   svm_fifo_chunk_t *c;
 
   ASSERT (fss_chunk_fl_index_is_valid (fss, fl_index));
 
-  fss_chunk_freelist_lock (fss);
+  old_head = clib_atomic_load_acq_n (&fss->free_chunks[fl_index]);
 
-  if (!fss->free_chunks[fl_index])
+  /* Lock-free stacks are affected by ABA if a side allocates a chunk and
+   * shortly thereafter frees it. To circumvent that, reuse the upper bits
+   * of the head of the list shared pointer, i.e., offset to where the chunk
+   * is, as a tag. The tag is incremented with each push/pop operation and
+   * therefore collisions can only happen if an element is popped and pushed
+   * exactly after a complete wrap of the tag (16 bits). It's unlikely either
+   * of the sides will be descheduled for that long */
+  do
     {
-      fss_chunk_freelist_unlock (fss);
-      return 0;
+      if (!(old_head & FS_CL_HEAD_MASK))
+	return 0;
+      c = fs_chunk_ptr (fsh, old_head & FS_CL_HEAD_MASK);
+      new_head = c->next + ((old_head + FS_CL_HEAD_TINC) & FS_CL_HEAD_TMASK);
     }
-
-  c = fs_chunk_ptr (fsh, fss->free_chunks[fl_index]);
-  fss->free_chunks[fl_index] = c->next;
-
-  fss_chunk_freelist_unlock (fss);
+  while (!__atomic_compare_exchange (&fss->free_chunks[fl_index], &old_head,
+				     &new_head, 0 /* weak */, __ATOMIC_RELEASE,
+				     __ATOMIC_ACQUIRE));
 
   return c;
 }
@@ -275,7 +295,7 @@ fss_fl_chunk_bytes_sub (fifo_segment_slice_t * fss, uword size)
 int
 fifo_segment_init (fifo_segment_t * fs)
 {
-  u32 align = 8, offset = 2 * 4096, slices_sz, i;
+  u32 align = 8, offset = FIFO_SEGMENT_ALLOC_OVERHEAD, slices_sz, i;
   uword max_fifo, seg_start, seg_sz;
   fifo_segment_header_t *fsh;
   ssvm_shared_header_t *sh;
@@ -678,7 +698,8 @@ free_list:
       if (data_bytes <= fss_fl_chunk_bytes (fss) + n_free)
 	{
 	  u32 min_size = FIFO_SEGMENT_MIN_FIFO_SIZE;
-
+	  if (n_free < min_size)
+	    goto done;
 	  batch = (data_bytes - fss_fl_chunk_bytes (fss)) / min_size;
 	  batch = clib_min (batch + 1, n_free / min_size);
 	  if (fsh_try_alloc_chunk_batch (fsh, fss, 0, batch))
@@ -883,6 +904,14 @@ fifo_segment_alloc_fifo_w_offset (fifo_segment_t *fs, uword offset)
   return f;
 }
 
+svm_fifo_t *
+fifo_segment_duplicate_fifo (fifo_segment_t *fs, svm_fifo_t *f)
+{
+  svm_fifo_t *nf = fs_fifo_alloc (fs, 0);
+  clib_memcpy (nf, f, sizeof (*f));
+  return nf;
+}
+
 /**
  * Free fifo allocated in fifo segment
  */
@@ -1022,6 +1051,30 @@ fifo_segment_fifo_offset (svm_fifo_t *f)
   return (u8 *) f->shr - (u8 *) f->fs_hdr;
 }
 
+svm_fifo_chunk_t *
+fifo_segment_alloc_chunk_w_slice (fifo_segment_t *fs, u32 slice_index,
+				  u32 chunk_size)
+{
+  fifo_segment_header_t *fsh = fs->h;
+  fifo_segment_slice_t *fss;
+
+  fss = fsh_slice_get (fsh, slice_index);
+  return fsh_try_alloc_chunk (fsh, fss, chunk_size);
+}
+
+void
+fifo_segment_collect_chunk (fifo_segment_t *fs, u32 slice_index,
+			    svm_fifo_chunk_t *c)
+{
+  fsh_collect_chunks (fs->h, slice_index, c);
+}
+
+uword
+fifo_segment_chunk_offset (fifo_segment_t *fs, svm_fifo_chunk_t *c)
+{
+  return (u8 *) c - (u8 *) fs->h;
+}
+
 svm_msg_q_t *
 fifo_segment_msg_q_alloc (fifo_segment_t *fs, u32 mq_index,
 			  svm_msg_q_cfg_t *cfg)
@@ -1271,7 +1324,7 @@ fs_slice_num_free_chunks (fifo_segment_header_t *fsh,
     {
       for (i = 0; i < FS_CHUNK_VEC_LEN; i++)
 	{
-	  c = fs_chunk_ptr (fsh, fss->free_chunks[i]);
+	  c = fss_chunk_free_list_head (fsh, fss, i);
 	  if (c == 0)
 	    continue;
 
@@ -1290,7 +1343,7 @@ fs_slice_num_free_chunks (fifo_segment_header_t *fsh,
   if (fl_index >= FS_CHUNK_VEC_LEN)
     return 0;
 
-  c = fs_chunk_ptr (fsh, fss->free_chunks[fl_index]);
+  c = fss_chunk_free_list_head (fsh, fss, fl_index);
   if (c == 0)
     return 0;
 
@@ -1324,16 +1377,16 @@ fifo_segment_size (fifo_segment_t * fs)
   return fs->h->max_byte_index - fs->h->n_reserved_bytes;
 }
 
-u8
-fsh_has_reached_mem_limit (fifo_segment_header_t * fsh)
+static u8
+fs_has_reached_mem_limit (fifo_segment_t *fs)
 {
-  return (fsh->flags & FIFO_SEGMENT_F_MEM_LIMIT) ? 1 : 0;
+  return (fs->flags & FIFO_SEGMENT_F_MEM_LIMIT) ? 1 : 0;
 }
 
-void
-fsh_reset_mem_limit (fifo_segment_header_t * fsh)
+static void
+fs_reset_mem_limit (fifo_segment_t *fs)
 {
-  fsh->flags &= ~FIFO_SEGMENT_F_MEM_LIMIT;
+  fs->flags &= ~FIFO_SEGMENT_F_MEM_LIMIT;
 }
 
 void *
@@ -1408,26 +1461,26 @@ fifo_segment_get_mem_usage (fifo_segment_t * fs)
 }
 
 fifo_segment_mem_status_t
-fifo_segment_determine_status (fifo_segment_header_t * fsh, u8 usage)
+fifo_segment_determine_status (fifo_segment_t *fs, u8 usage)
 {
-  if (!fsh->high_watermark || !fsh->low_watermark)
+  if (!fs->high_watermark || !fs->low_watermark)
     return MEMORY_PRESSURE_NO_PRESSURE;
 
   /* once the no-memory is detected, the status continues
    * until memory usage gets below the high watermark
    */
-  if (fsh_has_reached_mem_limit (fsh))
+  if (fs_has_reached_mem_limit (fs))
     {
-      if (usage >= fsh->high_watermark)
+      if (usage >= fs->high_watermark)
 	return MEMORY_PRESSURE_NO_MEMORY;
       else
-	fsh_reset_mem_limit (fsh);
+	fs_reset_mem_limit (fs);
     }
 
-  if (usage >= fsh->high_watermark)
+  if (usage >= fs->high_watermark)
     return MEMORY_PRESSURE_HIGH_PRESSURE;
 
-  else if (usage >= fsh->low_watermark)
+  else if (usage >= fs->low_watermark)
     return MEMORY_PRESSURE_LOW_PRESSURE;
 
   return MEMORY_PRESSURE_NO_PRESSURE;
@@ -1436,10 +1489,9 @@ fifo_segment_determine_status (fifo_segment_header_t * fsh, u8 usage)
 fifo_segment_mem_status_t
 fifo_segment_get_mem_status (fifo_segment_t * fs)
 {
-  fifo_segment_header_t *fsh = fs->h;
   u8 usage = fifo_segment_get_mem_usage (fs);
 
-  return fifo_segment_determine_status (fsh, usage);
+  return fifo_segment_determine_status (fs, usage);
 }
 
 u8 *
@@ -1519,7 +1571,7 @@ format_fifo_segment (u8 * s, va_list * args)
       fss = fsh_slice_get (fsh, slice_index);
       for (i = 0; i < FS_CHUNK_VEC_LEN; i++)
 	{
-	  c = fs_chunk_ptr (fsh, fss->free_chunks[i]);
+	  c = fss_chunk_free_list_head (fsh, fss, i);
 	  if (c == 0 && fss->num_chunks[i] == 0)
 	    continue;
 	  count = 0;
@@ -1546,7 +1598,7 @@ format_fifo_segment (u8 * s, va_list * args)
   in_use = fifo_segment_size (fs) - est_free_seg_bytes - tracked_cached_bytes;
   usage = (100.0 * in_use) / allocated;
   mem_st = fifo_segment_get_mem_status (fs);
-  virt = fsh_virtual_mem (fsh);
+  virt = fs_virtual_mem (fs);
   reserved = fsh->n_reserved_bytes;
 
   s = format (s, "\n%Useg free bytes: %U (%lu) estimated: %U (%lu) reserved:"