[dpdk-dev] DPDK compress API - questions

[Trahe, Fiona]

From: Matan Azrad <matan at nvidia.com> 
Sent: Wednesday, January 6, 2021 3:57 PM
To: Trahe, Fiona <fiona.trahe at intel.com>; ashish.gupta at marvell.com
Cc: dev at dpdk.org; NBU-Contact-Thomas Monjalon <thomas at monjalon.net>
Subject: DPDK compress API - questions

Hi Fiona, Ashish

I'm going to add new HW offload compress PMD for mlx5 devices in 21.02.

I have some questions on the API:

#define RTE_COMP_FF_NONCOMPRESSED_BLOCKS        (1ULL << 11)
/**< Creation of non-compressed blocks using RTE_COMP_LEVEL_NONE is supported */


1. What does it mean non-compressed block ? DMA?
[Fiona] Not exactly. E.g. for Deflate, if the output is non-compressed blocks, it still has the deflate headers.
So is not a direct DMA of the input data. As this may not be supported by all PMDs it is exposed in a feature flag.

2. Does Using RTE_COMP_LEVEL_NONE or RTE_COMP_ALGO_NULL the same?
[Fiona] No. ALGO_NULL would be DMA.
/**< No compression.
	 * Pass-through, data is copied unchanged from source buffer to
	 * destination buffer.
	 */
LEVEL_NONE should output the data in the correct format for the specified algorithm.

Probably I will add more question later.

Thanks
Matan