[SPDK] Re: AIO unmap support

Hi,

Linux AIO does not support asynchronous trim/unmap operations.  Using a synchronous interface would mean that the polled mode thread issuing the operation would be completely blocked until the operation was complete.

It could be possible to support unmap w/ AIO by creating a thread pool that is affinitized to some core(s) that are not occupied by polled mode threads.  The polled mode thread would need to pass a message to one of these threads to perform the unmap operation, and then receive a message back when the thread has completed its synchronous unmap operation.

-Jim


On 11/19/20, 7:44 AM, "khristenko.vladimir1986(a)gmail.com" <khristenko.vladimir1986(a)gmail.com> wrote:

    Environment:
     * SPDK v20.10
     * OS Centos8.2 
     * SSD Intel DC S4600 https://ark.intel.com/content/www/us/en/ark/products/120522/intel-ssd-dc-s4600-series-480gb-2-5in-sata-6gb-s-3d1-tlc.html

    My SSD support trim, but when I add it as AIO bdev I see that unmup not supported:
    #scripts/rpc.py bdev_aio_create /dev/sdf AIO0 
    # scripts/rpc.py bdev_get_bdevs
    [
      {
        "name": "AIO0",
        "aliases": [],
        "product_name": "AIO disk",
        "block_size": 512,
        "num_blocks": 937703088,
        "uuid": "78b0d637-87ca-49ad-80ec-95c614a66685",
       ...
        },
        "claimed": false,
        "zoned": false,
        "supported_io_types": {
          "read": true,
          "write": true,
          "unmap": false,
          "write_zeroes": true,
          "flush": true,
          "reset": true,
          "nvme_admin": false,
          "nvme_io": false
        },
        "driver_specific": {
          "aio": {
            "filename": "/dev/sdf"
          }
        }
      }
    ]

    Is there any opportunity to enable the unmap support for AIO bdev?
    If not, is it possible to implement the unmap support for AIO in the near future?

    Thank you.
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