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

Giovanni Cabiddu
2024-04-26T11:10:00Z

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% |
+---------------------------+---------+---------+---------+---------+

From the results we see that BTRFS with QAT configured for zlib-deflate Level 9
provides the best throughput with less CPU utilization and better compression
ratio compared with software zstd-l3, zlib-l3 and lzo.

Limitations:
* The implementation is synchronous, even if acomp is an asynchronous API.
* The implementation tries always to use an acomp tfm even if only
zlib-deflate-scomp is present. This ignores the compression levels
configuration for zlib.
* There is no way to configure a compression level for acomp(zlib-deflate).
This is hardcoded in the acomp algorithm implementation/provider.

[1] https://lore.kernel.org/all/1467083180-111750-1-git-send-email-weigang.li@intel.com/
[2] https://lore.kernel.org/all/ZO8ULhlJSrJ0Mcsx@gondor.apana.org.au/

Giovanni Cabiddu (5):
Revert "crypto: testmgr - Remove zlib-deflate"
Revert "crypto: deflate - Remove zlib-deflate"
Revert "crypto: qat - Remove zlib-deflate"
Revert "crypto: qat - remove unused macros in qat_comp_alg.c"
crypto: qat - change compressor settings for QAT GEN4

Weigang Li (1):
btrfs: zlib: add support for zlib-deflate through acomp

crypto/deflate.c | 61 +++--
crypto/testmgr.c | 10 +
crypto/testmgr.h | 75 ++++++
.../crypto/intel/qat/qat_common/adf_gen4_dc.c | 4 +-
.../intel/qat/qat_common/qat_comp_algs.c | 138 ++++++++++-
fs/btrfs/zlib.c | 216 ++++++++++++++++++
6 files changed, 484 insertions(+), 20 deletions(-)

base-commit: ed265f7fd9a635d77c8022fc6d9a1b735dd4dfd7
--
2.44.0