path: root/doc
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authorFiona Trahe <>2018-10-31 21:46:57 +0000
committerAkhil Goyal <>2018-11-02 12:26:06 +0100
commit4e8f2d6a6aaebe3f89f3edd09d479434f374a763 (patch)
treea614864668f339a84f05ead68f4c12f96f37e537 /doc
parent466a2c4bb5f4b9495380b1661d51047649d7fa76 (diff)
compress/qat: add log for IM buffer too small
Display trace if error returned from firmware is likely due to intermediate buffers being too small for the compressed output. Update documentation to explain this error case and to clarify intermediate buffer memory usage. Signed-off-by: Fiona Trahe <> Acked-by: Tomasz Jozwiak <>
Diffstat (limited to 'doc')
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 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