Hello Grant, Kyle, et al.,
Iirc the number of io_tlb enties on this u2/uturn ioa is of 256?
Because issue occur only when I do a lot of I/O on scsi disk (sometime request
of mapping reach 128 pages), the idea was that it could induce some exceed of
iotlb entries.
I so turn on some STAT (just used_pages) and grab following data:
[snip]
IO PDIR size : 131072 bytes (16384 entries)
IO PDIR entries : 16384 total 170 used (16214 free, 1%)
Resource bitmap : 2048 bytes (16384 pages)
Bitmap search : 36221/36430/38793 (min/avg/max CPU Cycles)
IO PDIR size : 131072 bytes (16384 entries)
IO PDIR entries : 16384 total 235 used (16149 free, 1%)
Resource bitmap : 2048 bytes (16384 pages)
Bitmap search : 36220/36346/37806 (min/avg/max CPU Cycles)
IO PDIR size : 131072 bytes (16384 entries)
IO PDIR entries : 16384 total 718 used (15666 free, 4%)
Resource bitmap : 2048 bytes (16384 pages)
Bitmap search : 36222/36342/38472 (min/avg/max CPU Cycles)
## issue occurs just when I ready above message.
IO PDIR size : 131072 bytes (16384 entries)
IO PDIR entries : 16384 total 444 used (15940 free, 2%)
Resource bitmap : 2048 bytes (16384 pages)
Bitmap search : 36220/36330/37830 (min/avg/max CPU Cycles)
[snip]
Even thought, I ended the stress test, the system continue to work smoothly
with 444 used entries?
Anyway, difference between those last 2 samples (718 - 444) = 274 increase of
io_pdir entries.
I also add a loop to bitcount entries of res_map and grab more:
[snip]
IO PDIR size : 262144 bytes (32768 entries)
IO PDIR entries : 32768 total 329 used (32439 free, 1%)
IO PDIR entries : 329 res_map_count
Resource bitmap : 4096 bytes (32768 pages)
Bitmap search : 36221/36626/38310 (min/avg/max CPU Cycles)
IO PDIR size : 262144 bytes (32768 entries)
IO PDIR entries : 32768 total 801 used (31967 free, 2%)
IO PDIR entries : 801 res_map_count
Resource bitmap : 4096 bytes (32768 pages)
Bitmap search : 36215/36325/37852 (min/avg/max CPU Cycles)
IO PDIR size : 262144 bytes (32768 entries)
IO PDIR entries : 32768 total 329 used (32439 free, 1%)
IO PDIR entries : 329 res_map_count
Resource bitmap : 4096 bytes (32768 pages)
Bitmap search : 36222/36883/38742 (min/avg/max CPU Cycles)
[...]
(in 1 second 801 - 329 = 472)
But continuing a bit test (by accident), I noticed that system can survive with:
IO PDIR size : 262144 bytes (32768 entries)
IO PDIR entries : 32768 total 1478 used (31290 free, 4%)
IO PDIR entries : 1478 res_map_count
Resource bitmap : 4096 bytes (32768 pages)
Bitmap search : 36223/36696/38463 (min/avg/max CPU Cycles)
Well as scatterlist is still puzzling me, I can still be confused between
iommu and mmu pages mapping, sorry so in advance if it's yet another annoying
comment.
Tx again,
J.
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