mirror of
https://github.com/varun-r-mallya/sysprof.git
synced 2025-12-31 20:36:25 +00:00
Use two consecutive mappings of the ring buffer.
This allows us to not ignore wrapping and just process events instead of having to copy the data to temporary storage.
This commit is contained in:
Søren Sandmann Pedersen
171
collector.c
171
collector.c
@ -127,130 +127,92 @@ sysprof_perf_counter_open (struct perf_counter_attr *attr,
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return syscall (__NR_perf_counter_open, attr, pid, cpu, group_fd, flags);
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}
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static int
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process_event (counter_t *counter, void *data)
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{
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struct perf_event_header *header = data;
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counter->callback ((counter_event_t *)header, counter->user_data);
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return header->size;
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}
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static int
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n_missing_bytes (const uint8_t *data, int n_bytes)
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{
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const struct perf_event_header *header;
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if (n_bytes < sizeof (*header))
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return sizeof (*header) - n_bytes;
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header = (const void *)data;
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if (n_bytes < header->size)
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return header->size - n_bytes;
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return 0;
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}
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static void
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process_events (counter_t *counter, uint8_t *data, int n_bytes,
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GString *partial)
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{
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int n_events;
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ssize_t n_missing;
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n_events = 0;
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while (n_bytes && (n_missing = n_missing_bytes (
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(uint8_t *)partial->str, partial->len)))
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{
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n_missing = MIN (n_bytes, n_missing);
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g_string_append_len (partial, (const char *)data, n_missing);
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data += n_missing;
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n_bytes -= n_missing;
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}
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if (partial->len)
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{
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int n_used;
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if (n_missing_bytes ((uint8_t *)partial->str, partial->len))
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return;
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n_used = process_event (counter, partial->str);
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g_assert (n_used == partial->len);
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g_string_truncate (partial, 0);
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}
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while (n_bytes && !n_missing_bytes (data, n_bytes))
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{
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int n_used = process_event (counter, data);
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data += n_used;
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n_bytes -= n_used;
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}
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if (n_missing_bytes (data, n_bytes))
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g_string_append_len (partial, (char *)data, n_bytes);
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}
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static void
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on_read (gpointer data)
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{
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uint64_t head, tail;
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counter_t *counter = data;
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int mask = (N_PAGES * process_get_page_size() - 1);
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uint64_t size;
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int diff;
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#if 0
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int n_bytes = mask + 1;
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int x;
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#endif
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tail = counter->tail;
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head = counter->mmap_page->data_head;
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rmb();
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diff = head - tail;
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if (diff < 0)
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if (head < tail)
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{
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g_warning ("sysprof fails at reading the buffer\n");
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g_warning ("sysprof fails at ring buffers\n");
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tail = head;
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}
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size = head - tail;
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#if 0
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/* Verify that the double mapping works */
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x = g_random_int() & mask;
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g_assert (*(counter->data + x) == *(counter->data + x + n_bytes));
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#endif
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if ((tail & mask) + size != (head & mask))
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while (head - tail >= sizeof (struct perf_event_header))
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{
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size = mask + 1 - (tail & mask);
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g_assert ((tail & mask) + size <= (N_PAGES * process_get_page_size()));
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process_events (counter, counter->data + (tail & mask),
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size, counter->partial);
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tail += size;
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struct perf_event_header *header = (void *)(counter->data + (tail & mask));
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if (header->size > head - tail)
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{
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g_print ("asdf\n");
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break;
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}
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counter->callback ((counter_event_t *)header, counter->user_data);
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tail += header->size;
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}
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size = head - tail;
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g_assert ((tail & mask) + size <= (N_PAGES * process_get_page_size()));
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process_events (counter,
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counter->data + (tail & mask), size, counter->partial);
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tail += size;
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counter->tail = tail;
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counter->mmap_page->data_tail = tail;
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}
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#define fail(x)
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/* FIXME: return proper errors */
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#define fail(x) \
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do { \
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g_printerr ("the fail is strong %s\n", x); \
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exit (-1); \
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} while (0)
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static void *
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map_buffer (counter_t *counter)
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{
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int n_bytes = N_PAGES * process_get_page_size();
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void *address, *a;
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address = mmap (NULL, n_bytes * 2 + process_get_page_size(), PROT_NONE,
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MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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if (address == MAP_FAILED)
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fail ("mmap");
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a = mmap (address + n_bytes, n_bytes + process_get_page_size(),
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PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_FIXED, counter->fd, 0);
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if (a != address + n_bytes)
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fail ("mmap");
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a = mmap (address, n_bytes + process_get_page_size(),
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PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_FIXED, counter->fd, 0);
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if (a == MAP_FAILED)
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fail ("mmap");
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if (a != address)
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fail ("mmap");
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return address;
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}
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static counter_t *
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counter_new (int cpu,
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@ -283,11 +245,10 @@ counter_new (int cpu,
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fail ("perf_counter_open");
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return NULL;
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}
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counter->fd = fd;
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counter->mmap_page = mmap (
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NULL, (N_PAGES + 1) * process_get_page_size(),
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PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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counter->mmap_page = map_buffer (counter);
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if (counter->mmap_page == MAP_FAILED)
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{
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