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libsysprof-capture: remove framing data from MappedRingBuffer

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This removes the 8 bytes of framing data from the MappedRingBuffer which
means we can write more data without racing. But also this means that we
can eventually use the mapped ring buffer as our normal buffer for
capture writing (to be done later).
This commit is contained in:
Christian Hergert
2020-02-15 20:46:05 -07:00
parent e7f2702f88
commit e3ed30eb48
4 changed files with 111 additions and 100 deletions
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60
src/libsysprof-capture/mapped-ring-buffer.c
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@ -40,18 +40,6 @@ enum {
MODE_WRITER = 2,
};
/*
* MappedRingFrame is the header on each buffer entry so that
* we can stay 8-byte aligned.
*/
typedef struct _MappedRingFrame
{
guint64 len : 32;
guint64 padding : 32;
} MappedRingFrame;
G_STATIC_ASSERT (sizeof (MappedRingFrame) == 8);
/*
* MappedRingHeader is the header of the first page of the
* buffer. We use the whole buffer so that we can double map
@ -90,7 +78,7 @@ static inline gpointer
get_body_at_pos (MappedRingBuffer *self,
gsize pos)
{
g_assert (pos < (self->body_size + self->body_size - sizeof (MappedRingFrame)));
g_assert (pos < (self->body_size + self->body_size));
return (guint8 *)self->map + self->page_size + pos;
}
@ -380,8 +368,6 @@ mapped_ring_buffer_allocate (MappedRingBuffer *self,
g_return_val_if_fail (length < self->body_size, NULL);
g_return_val_if_fail ((length & 0x7) == 0, NULL);
length += sizeof (MappedRingFrame);
header = get_header (self);
headpos = g_atomic_int_get (&header->head);
tailpos = g_atomic_int_get (&header->tail);
@ -396,13 +382,13 @@ mapped_ring_buffer_allocate (MappedRingBuffer *self,
*/
if (tailpos == headpos)
return get_body_at_pos (self, tailpos + sizeof (MappedRingFrame));
return get_body_at_pos (self, tailpos);
if (headpos < tailpos)
headpos += self->body_size;
if (tailpos + length < headpos)
return get_body_at_pos (self, tailpos + sizeof (MappedRingFrame));
return get_body_at_pos (self, tailpos);
return NULL;
}
@ -430,7 +416,6 @@ mapped_ring_buffer_advance (MappedRingBuffer *self,
gsize length)
{
MappedRingHeader *header;
MappedRingFrame *fr;
guint32 tail;
g_return_if_fail (self != NULL);
@ -442,13 +427,8 @@ mapped_ring_buffer_advance (MappedRingBuffer *self,
header = get_header (self);
tail = header->tail;
/* First write the frame header with the data length */
fr = get_body_at_pos (self, tail);
fr->len = length;
fr->padding = 0;
/* Now calculate the new tail position */
tail = tail + sizeof *fr + length;
/* Calculate the new tail position */
tail = tail + length;
if (tail >= self->body_size)
tail -= self->body_size;
@ -508,13 +488,16 @@ mapped_ring_buffer_drain (MappedRingBuffer *self,
while (headpos < tailpos)
{
const MappedRingFrame *fr = get_body_at_pos (self, headpos);
gconstpointer data = (guint8 *)fr + sizeof *fr;
gconstpointer data = get_body_at_pos (self, headpos);
gsize len = tailpos - headpos;
headpos = headpos + sizeof *fr + fr->len;
if (!callback (data, fr->len, user_data))
if (!callback (data, &len, user_data))
goto short_circuit;
if (len > (tailpos - headpos))
goto short_circuit;
headpos += len;
}
ret = TRUE;
@ -605,9 +588,10 @@ static GSourceFuncs mapped_ring_source_funcs = {
};
guint
mapped_ring_buffer_create_source (MappedRingBuffer *self,
MappedRingBufferCallback source_func,
gpointer user_data)
mapped_ring_buffer_create_source_full (MappedRingBuffer *self,
MappedRingBufferCallback source_func,
gpointer user_data,
GDestroyNotify destroy)
{
MappedRingSource *source;
@ -618,8 +602,16 @@ mapped_ring_buffer_create_source (MappedRingBuffer *self,
source = (MappedRingSource *)g_source_new (&mapped_ring_source_funcs, sizeof (MappedRingSource));
source->self = mapped_ring_buffer_ref (self);
g_source_set_callback ((GSource *)source, (GSourceFunc)source_func, user_data, NULL);
g_source_set_callback ((GSource *)source, (GSourceFunc)source_func, user_data, destroy);
g_source_set_name ((GSource *)source, "MappedRingSource");
return g_source_attach ((GSource *)source, g_main_context_default ());
}
guint
mapped_ring_buffer_create_source (MappedRingBuffer *self,
MappedRingBufferCallback source_func,
gpointer user_data)
{
return mapped_ring_buffer_create_source_full (self, source_func, user_data, NULL);
}