Ingo Schneider wrote:
> I made a patch which lets the user specify the size of the DMA buffer
> which should be used.
> I coded a warning at a buffer usage of 80%.
If you really need this warning you have to ensure that it cannot flood
the syslog, i.e. you have to implement some kind of rate limiting.
> Also, the default size was increased to 470k, I made a lot of tests
> using different buffer widths and heights.
Unless you can test _all_ card types supported by the budget family
you should better not change the default behaviour. ;-)
> I found out that the max DMA buffer used was 2328 TS packets.
> With this patch I got no dropouts at all when recording 6 streams with
> VDR, making a backup between 2 disks and doing some random sync's.
> I still have to disable the local APIC in bios though.
I still believe that your system has a severe problem...
Some specific comments:
>+module_param_named(bufsize, budget_buffer_size, int, 0644);
++++
Must be 0444 because it cannot be changed at runtime.
If possible avoid macros except for constants:
>+#define TS_WIDTH(budget) (budget->buffer_width)
>+#define TS_HEIGHT(budget) (budget->buffer_height)
>+#define TS_BUFLEN(budget) (budget->buffer_width * budget->buffer_height)
>+#define TS_MAX_PACKETS(budget) (TS_BUFLEN(budget)/TS_SIZE)
For better readability and to avoid computations in the ISR just use
- budget->buffer_width
- budget->buffer_heigth
- budget->buffer_length
- budget->max_packets
and drop those macros completely.
Please avoid unnecessary calculations at run-time:
> dvb_dmx_swfilter_packets(&budget->demux, mem + olddma, (newdma - olddma) / 188);
>+ count = (newdma - olddma) / 188;
should be replaced by
| count = (newdma - olddma) / 188;
| dvb_dmx_swfilter_packets(&budget->demux, mem + olddma, count);
(The compiler might detect and optimize common sub-expressions but we
cannot be sure.)
>+ if (bufsize / budget->buffer_width > TS_MAX_HEIGHT && budget->card->type != BUDGET_FS_ACTIVY) // keep width constant as long if possible
>+ budget->buffer_width = BUDGET_MOD_LIMIT(bufsize/TS_MAX_HEIGHT, TS_MOD_WIDTH, TS_MAX_WIDTH);
>+
>+ budget->buffer_height = BUDGET_MOD_LIMIT(bufsize/budget->buffer_width, TS_MOD_HEIGHT, TS_MAX_HEIGHT);
Please add a comment: Explain what you are trying to do here.
Can we really be sure that it works with all cards (except ACTIVY)?
>+ printk("budget: width = %d, height = %d\n", budget->buffer_width, budget->buffer_height);
Debug message? -> dprintk
Oliver
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