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-rw-r--r--doc/guides/cryptodevs/qat.rst23
1 files changed, 20 insertions, 3 deletions
diff --git a/doc/guides/cryptodevs/qat.rst b/doc/guides/cryptodevs/qat.rst
index b2dfeb0..1db9868 100644
--- a/doc/guides/cryptodevs/qat.rst
+++ b/doc/guides/cryptodevs/qat.rst
@@ -156,6 +156,7 @@ These are the build configuration options affecting QAT, and their default value
CONFIG_RTE_LIBRTE_PMD_QAT_SYM=n
CONFIG_RTE_PMD_QAT_MAX_PCI_DEVICES=48
CONFIG_RTE_PMD_QAT_COMP_SGL_MAX_SEGMENTS=16
+ CONFIG_RTE_PMD_QAT_COMP_IM_BUFFER_SIZE=65536
CONFIG_RTE_LIBRTE_PMD_QAT must be enabled for any QAT PMD to be built.
@@ -168,14 +169,30 @@ options and is built by default.
The number of VFs per PF varies - see table below. If multiple QAT packages are
installed on a platform then CONFIG_RTE_PMD_QAT_MAX_PCI_DEVICES should be
adjusted to the number of VFs which the QAT common code will need to handle.
-Note, there is a separate config item for max cryptodevs CONFIG_RTE_CRYPTO_MAX_DEVS,
-if necessary this should be adjusted to handle the total of QAT and other devices
-which the process will use.
+Note, there are separate config items for max cryptodevs CONFIG_RTE_CRYPTO_MAX_DEVS
+and max compressdevs CONFIG_RTE_COMPRESS_MAX_DEVS, if necessary these should be
+adjusted to handle the total of QAT and other devices which the process will use.
QAT allocates internal structures to handle SGLs. For the compression service
CONFIG_RTE_PMD_QAT_COMP_SGL_MAX_SEGMENTS can be changed if more segments are needed.
An extra (max_inflight_ops x 16) bytes per queue_pair will be used for every increment.
+QAT compression PMD needs intermediate buffers to support Deflate compression
+with Dynamic Huffman encoding. CONFIG_RTE_PMD_QAT_COMP_IM_BUFFER_SIZE
+specifies the size of a single buffer, the PMD will allocate a multiple of these,
+plus some extra space for associated meta-data. For GEN2 devices, 20 buffers plus
+1472 bytes are allocated.
+
+.. Note::
+
+ If the compressed output of a Deflate operation using Dynamic Huffman
+ Encoding is too big to fit in an intermediate buffer, then the
+ operation will return RTE_COMP_OP_STATUS_ERROR and an error will be
+ displayed. Options for the application in this case
+ are to split the input data into smaller chunks and resubmit
+ in multiple operations or to configure QAT with
+ larger intermediate buffers.
+
Device and driver naming
~~~~~~~~~~~~~~~~~~~~~~~~