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From: "Pai G, Sunil" <sunil.pai.g@intel.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"Laatz, Kevin" <kevin.laatz@intel.com>,
	"stable@dpdk.org" <stable@dpdk.org>,
	"Hu, Jiayu" <jiayu.hu@intel.com>
Subject: RE: [PATCH] dma/idxd: fix burst capacity calculation
Date: Mon, 10 Jan 2022 13:44:06 +0000	[thread overview]
Message-ID: <DM8PR11MB56050FA06795ECBC51354370BD509@DM8PR11MB5605.namprd11.prod.outlook.com> (raw)
In-Reply-To: <YdwzvhBUdCXWJ669@bricha3-MOBL.ger.corp.intel.com>

Hi Bruce,

> what values for the write_idx and ids_returned vars give this error, and how
> does masking help? I'd expect masking to increase the number of times the
> function returns zero, rather than decreasing it.


Here are the values from the idxd dump:
dev_capa: 0x500000051 - mem2mem sva handles_errors copy fill
max_vchans_supported: 1
nb_vchans_configured: 1
silent_mode: off
 IDXD Private Data ==
Portal: 0x7ffff7ffb000
Config: { ring_size: 4096 }
Batch ring (sz = 129, max_batches = 128):
62370  62402  62434  62466  62498  62530  62562  62594  62626  62658  62690  62722  62754  62786  62818  62850  62882  62914  62946  62978  63010  63042  63074  6
3106  63138  63170  63202  63234  63266  63298  63330  63362  63394  63426  63458  63490  63522  63554  63586  63618  63650  63682  63714  63746  63778  63810  63842  63874  63906  63938  63970  64002  64034  64066  64098  6413
0  64162  64194  64226  64258  64290  64322  64354  64386  64418  64450  64482  64514  64546  64578  64610  64642  64674  64706  64738  64770  64802  64834  64866  64898  64930  64962  64994  65026  65058  65090  65122  65154  
65186  65218  65250  65282  65314  65346  65378  65410  65442  65474  65506 [rd ptr]  2 [wr ptr]  61442  61474  61506  61538  61570  61602  61634  61666  61698  61730  61762  61794  61826  61858  61890  61922  61954  61986  620
18  62050  62082  62114  62146  62178  62210  62242  62274  62306  62338
  Curr batch: start = 2, size = 0
  IDS: avail = 65506, returned: 65506
max packets per batch from hw: 1024
batches left: 127, ring space left: 4064
idxd->desc_ring_mask: 4095, used_space: 4128, used_space: 4128, idxd->max_batch_size: 1024, idxd->batch_size: 0
write_idx: 4098, idxd->batch_idx_read: 98, idxd->batch_idx_write: 99, idxd->desc_ring_mask - used_space: 65503

relevant data from above:
write_idx: 4098 , IDS returned: 65506, idxd->desc_ring_mask: 4095

without the fix :
used_space = write_idx - idxd->ids_returned; (4098 - 65506)   = -61408

with fix: 
used_space = (write_idx - idxd->ids_returned)& idxd->desc_ring_mask; (4098 - 65506)&4095   = 32 
which seems to match the rd ptr and wr ptr.

Thanks and regards,
Sunil

  reply	other threads:[~2022-01-10 13:44 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-20 17:05 Bruce Richardson
2022-01-04 17:16 ` Kevin Laatz
2022-01-05  1:32   ` Hu, Jiayu
2022-01-10 13:09 ` Pai G, Sunil
2022-01-10 13:25   ` Bruce Richardson
2022-01-10 13:44     ` Pai G, Sunil [this message]
2022-01-10 16:18       ` Bruce Richardson
2022-01-11 13:41 ` [PATCH v2 0/4] fixes for dma/idxd Bruce Richardson
2022-01-11 13:41   ` [PATCH v2 1/4] dma/idxd: fix burst capacity calculation Bruce Richardson
2022-01-11 13:41   ` [PATCH v2 2/4] dma/idxd: fix paths to driver sysfs directory Bruce Richardson
2022-01-11 16:50     ` Kevin Laatz
2022-01-11 13:41   ` [PATCH v2 3/4] dma/idxd: fix wrap-around in burst capacity calculation Bruce Richardson
2022-01-11 13:45     ` Pai G, Sunil
2022-01-11 16:50     ` Kevin Laatz
2022-01-11 13:41   ` [PATCH v2 4/4] test_dmadev: increase iterations of capacity test case Bruce Richardson
2022-01-11 16:50     ` Kevin Laatz
2022-01-20 13:06   ` [PATCH v2 0/4] fixes for dma/idxd Thomas Monjalon

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