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
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 (!clib_atomic_cmp_and_swap_acq_relax (
+ &fss->free_chunks[fl_index], &old_head, &new_head, 1 /* weak */));
}
static void
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 (!clib_atomic_cmp_and_swap_acq_relax (
+ &fss->free_chunks[fl_index], &old_head, &new_head, 1 /* weak */));
}
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 (!clib_atomic_cmp_and_swap_acq_relax (
+ &fss->free_chunks[fl_index], &old_head, &new_head, 1 /* weak */));
return c;
}
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))
vec_free (fs->slices);
vec_foreach (fs->mqs, mq)
- vec_free (mq->rings);
+ svm_msg_q_cleanup (mq);
vec_free (fs->mqs);
}
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)
{
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;
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;
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;
Code Review / vpp.git / blobdiff