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Thu, 19 Jun 2025 20:21:53 +0000 Date: Thu, 19 Jun 2025 21:21:46 +0100 From: Giovanni Cabiddu To: Herbert Xu CC: , , , Subject: Re: [PATCH] crypto: qat - lower priority for skcipher and aead algorithms Message-ID: References: <20250613103309.22440-1-giovanni.cabiddu@intel.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Organization: Intel Research and Development Ireland Ltd - Co. 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Or does it require physically > contiguous memory much greater than 4K in size? Yes, batching a large number of 4KiB requests is sufficient to achieve near-maximum throughput. In an experiment using the skcipher APIs in asynchronous mode, I was able to reach approximately 11 GB/s throughput with 4KiB buffers. To achieve this, I had to increase the request queue depth and adjust the interrupt coalescing timer, which is set quite high by default. I'm continuing to experiment. For example, I modified the code to send a direct pointer to the device when the source and destination scatterlist entries each contain only a single segment. This should reduce I/O overhead by avoiding the need to read the scatter-gather list descriptors. Regarding the synchronous use case, preliminary analysis shows that the main bottlenecks are: (1) interrupt handling — particularly the overhead of completion handling, with significant time spent in the tasklet executing crypto_req_done() and (2) latency waiting on the device. I'm exploring ways to improve these. While this work might seem moot given that AES is faster in the core, the same optimizations are applicable to the compression service, where QAT can still provide benefits. Regards, -- Giovanni