Skip to content

openipc_frame_ts: tunable ring_depth module_param (closes #200) #201

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
widgetii merged 1 commit into from
May 28, 2026
Merged

openipc_frame_ts: tunable ring_depth module_param (closes #200) #201

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
96 changes: 81 additions & 15 deletions kernel/openipc_frame_ts/openipc_frame_ts.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -39,12 +39,33 @@
#define OPENIPC_FT_MAX_CHN 8
#define OPENIPC_FT_MAX_EVT_TYPE 2 /* MIPI_FS + ISP_FEND so far */
/*
* Per-channel ring depth (power of 2). 256 events ≈ 0.5 s of buffer at
* 240 fps × 2 event types — covers high-fps modes (imx335 800x480 240 fps)
* with margin for reader-side jitter (scheduler latency, printf-to-disk).
* At 32 B/event the per-channel cost is 8 KiB.
* Per-channel ring depth bounds. Must be powers of two — push uses
* `head & (depth-1)` wrap math, which only works for power-of-2 depths.
*
* Default 256 ≈ 0.5 s buffer at 240 fps × 2 event types (8 KiB/chn). Fine
* for the SR-anchor use case (reads cached state every ~5 s and tolerates
* stale entries).
*
* For per-frame consumers — frame-by-frame latency histograms, evidence
* chains, multi-sensor sync correlators — the default may be undersized
* if the reader's dispatch latency is bursty (libevent under RTSP+RTCP
* load on cv500 was observed to lose ~52 events/s during 30 s sessions,
* see openhisilicon#200). Raise via `insmod open_openipc_frame_ts
* ring_depth=4096` (16× default, ~8 s buffer; 128 KiB/chn × 8 chn = 1 MiB
* total worst case).
*/
#define OPENIPC_FT_DEPTH 256
#define OPENIPC_FT_DEPTH_MIN 16
#define OPENIPC_FT_DEPTH_MAX 65536
#define OPENIPC_FT_DEPTH_DEFAULT 256

static unsigned int ring_depth = OPENIPC_FT_DEPTH_DEFAULT;
module_param(ring_depth, uint, 0444);
MODULE_PARM_DESC(ring_depth,
"Per-channel ring depth (power of 2, 16..65536, default 256). "
"Bump for per-frame consumers under bursty reader load.");

static unsigned int g_ring_depth;
static unsigned int g_ring_mask;
/*
* Drop double-pushes of the SAME event type within these intervals.
*
Expand Down Expand Up @@ -74,7 +95,7 @@ static const u64 openipc_ft_min_interval_ns[OPENIPC_FT_MAX_EVT_TYPE] = {
};

struct openipc_ft_chn {
struct openipc_frame_ts_event ring[OPENIPC_FT_DEPTH];
struct openipc_frame_ts_event *ring; /* kmalloc'd, g_ring_depth entries */
unsigned int head;
unsigned int tail;
u32 seq[OPENIPC_FT_MAX_EVT_TYPE];
Expand Down Expand Up @@ -170,12 +191,12 @@ static void strobe_on_event(unsigned int event_type)

static inline unsigned int ring_count(const struct openipc_ft_chn *c)
{
return (c->head - c->tail) & (OPENIPC_FT_DEPTH - 1);
return (c->head - c->tail) & g_ring_mask;
}

static inline bool ring_full(const struct openipc_ft_chn *c)
{
return ring_count(c) == (OPENIPC_FT_DEPTH - 1);
return ring_count(c) == g_ring_mask;
}

static inline bool ring_empty(const struct openipc_ft_chn *c)
Expand Down Expand Up @@ -216,7 +237,7 @@ void openipc_frame_ts_push(unsigned int vi_chn, unsigned int event_type)

if (ring_full(c)) {
/* drop oldest */
c->tail = (c->tail + 1) & (OPENIPC_FT_DEPTH - 1);
c->tail = (c->tail + 1) & g_ring_mask;
c->dropped++;
}
e = &c->ring[c->head];
Expand All @@ -226,7 +247,7 @@ void openipc_frame_ts_push(unsigned int vi_chn, unsigned int event_type)
e->seq = c->seq[event_type]++;
e->event_type = event_type;
e->reserved = 0;
c->head = (c->head + 1) & (OPENIPC_FT_DEPTH - 1);
c->head = (c->head + 1) & g_ring_mask;
spin_unlock_irqrestore(&c->lock, flags);

strobe_on_event(event_type);
Expand Down Expand Up @@ -312,7 +333,7 @@ static bool pop_one(u32 chn_mask, u32 evt_mask,
struct openipc_frame_ts_event *cand =
&c->ring[c->tail];

c->tail = (c->tail + 1) & (OPENIPC_FT_DEPTH - 1);
c->tail = (c->tail + 1) & g_ring_mask;
if (event_passes(cand, chn_mask, evt_mask)) {
*out = *cand;
got = true;
Expand Down Expand Up @@ -607,13 +628,43 @@ static const struct attribute_group strobe_attr_group = {
.attrs = strobe_attrs,
};

static unsigned int sanitize_ring_depth(unsigned int req)
{
unsigned int d = req;
unsigned int p;

if (d < OPENIPC_FT_DEPTH_MIN)
d = OPENIPC_FT_DEPTH_MIN;
if (d > OPENIPC_FT_DEPTH_MAX)
d = OPENIPC_FT_DEPTH_MAX;

/* round up to next power of 2 */
p = 1;
while (p < d)
p <<= 1;
return p;
}

static int __init openipc_ft_init(void)
{
unsigned int i;
int ret;

for (i = 0; i < OPENIPC_FT_MAX_CHN; i++)
g_ring_depth = sanitize_ring_depth(ring_depth);
g_ring_mask = g_ring_depth - 1;
if (g_ring_depth != ring_depth)
pr_info("openipc_frame_ts: ring_depth %u → %u (clamped + power-of-2)\n",
ring_depth, g_ring_depth);

for (i = 0; i < OPENIPC_FT_MAX_CHN; i++) {
g_chn[i].ring = kmalloc_array(g_ring_depth,
sizeof(struct openipc_frame_ts_event), GFP_KERNEL);
if (!g_chn[i].ring) {
ret = -ENOMEM;
goto err_free_rings;
}
spin_lock_init(&g_chn[i].lock);
}

init_waitqueue_head(&g_wait);

Expand All @@ -627,7 +678,7 @@ static int __init openipc_ft_init(void)
ret = misc_register(&g_miscdev);
if (ret) {
pr_err("openipc_frame_ts: misc_register failed: %d\n", ret);
return ret;
goto err_free_rings;
}

ret = sysfs_create_group(&g_miscdev.this_device->kobj,
Expand All @@ -636,20 +687,35 @@ static int __init openipc_ft_init(void)
pr_warn("openipc_frame_ts: strobe sysfs attrs not created: %d\n",
ret);

pr_info("openipc_frame_ts: /dev/%s minor=%d, event types=%u\n",
OPENIPC_FT_NAME, g_miscdev.minor, OPENIPC_FT_MAX_EVT_TYPE);
pr_info("openipc_frame_ts: /dev/%s minor=%d, event types=%u, ring_depth=%u\n",
OPENIPC_FT_NAME, g_miscdev.minor, OPENIPC_FT_MAX_EVT_TYPE,
g_ring_depth);
return 0;

err_free_rings:
while (i--) {
kfree(g_chn[i].ring);
g_chn[i].ring = NULL;
}
return ret;
}

static void __exit openipc_ft_exit(void)
{
unsigned int i;

sysfs_remove_group(&g_miscdev.this_device->kobj, &strobe_attr_group);
hrtimer_cancel(&g_strobe_timer);
mutex_lock(&g_strobe_lock);
g_strobe_mode = STROBE_OFF;
strobe_release_gpio_locked();
mutex_unlock(&g_strobe_lock);
misc_deregister(&g_miscdev);

for (i = 0; i < OPENIPC_FT_MAX_CHN; i++) {
kfree(g_chn[i].ring);
g_chn[i].ring = NULL;
}
}

module_init(openipc_ft_init);
Expand Down
Loading