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[RFC,0/6] btrfs: offload zlib-deflate to accelerators

Message ID 20240426110941.5456-1-giovanni.cabiddu@intel.com
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Series btrfs: offload zlib-deflate to accelerators | expand

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Giovanni Cabiddu April 26, 2024, 10:54 a.m. UTC 
Add support for zlib compression and decompression through the acomp
APIs in BTRFS. This enables [de]compression operations to be offloaded
to accelerators. This is a rework of [1].

This set also re-enables zlib-deflate in the Crypto API and in the QAT
driver as they were removed in [2] since there was no user in kernel.
The re-enablement is done by reverting the commits that removed such
feature.

The code has been benchmarked on a system with the following specs:
 * Dual socket Intel(R) Xeon(R) Platinum 8470N
 * 512GB (16x32GB DDR5 4800 MT/s [4800 MT/s])
 * 4 NVMe disks (349.3G INTEL SSDPE21K375GA)
 * 2 QAT 4xxx devices, one per socket, configured for compression only
 * Kernel 6.8.2

The test consisted of 4 processes running `dd` that wrote in parallel
50GB of data (Silesia corpus) to the 4 NVMe disks separately. We captured
disk write throughput, CPU utilization and compression ratio:

    +---------------------------+---------+---------+---------+---------+
    |                           | QAT-L9  | ZSTD-L3 | ZLIB-L3 | LZO-L1  |
    +---------------------------+---------+---------+---------+---------+
    | Disk Write TPUT (GiB/s)   | 6.5     | 5.2     | 2.2     | 6.5     |
    +---------------------------+---------+---------+---------+---------+
    | CPU utils %age @208 cores | 4.56%   | 15.67%  | 12.79%  | 19.85%  |
    +---------------------------+---------+---------+---------+---------+
    | Compression Ratio         | 34%     | 35%     | 37%     | 58%     |
    +---------------------------+---------+---------+---------+---------+