On 3/29/23 19:41, Nitesh Shetty wrote: >>> +What: /sys/block/<disk>/queue/copy_max_bytes >>> +Date: November 2022 >>> +Contact: linux-block@xxxxxxxxxxxxxxx >>> +Description: >>> + [RW] While 'copy_max_bytes_hw' is the hardware limit for the >>> + device, 'copy_max_bytes' setting is the software limit. >>> + Setting this value lower will make Linux issue smaller size >>> + copies from block layer. >> >> This is the maximum number of bytes that the block >> layer will allow for a copy request. Must be smaller than >> or equal to the maximum size allowed by the hardware indicated > > Looks good. Will update in next version. We took reference from discard. > >> by copy_max_bytes_hw. Write 0 to use the default kernel >> settings. >> > > Nack, writing 0 will not set it to default value. (default value is > copy_max_bytes = copy_max_bytes_hw) It is trivial to make it work that way, which would match how max_sectors_kb works. Write 0 to return copy_max_bytes being equal to the default copy_max_bytes_hw. The other possibility that is also interesting is "write 0 to disable copy offload and use emulation". This one may actually be more useful. > >>> + >>> + >>> +What: /sys/block/<disk>/queue/copy_max_bytes_hw >>> +Date: November 2022 >>> +Contact: linux-block@xxxxxxxxxxxxxxx >>> +Description: >>> + [RO] Devices that support offloading copy functionality may have >>> + internal limits on the number of bytes that can be offloaded >>> + in a single operation. The `copy_max_bytes_hw` >>> + parameter is set by the device driver to the maximum number of >>> + bytes that can be copied in a single operation. Copy >>> + requests issued to the device must not exceed this limit. >>> + A value of 0 means that the device does not >>> + support copy offload. >> >> [RO] This is the maximum number of kilobytes supported in a >> single data copy offload operation. A value of 0 means that the >> device does not support copy offload. >> > > Nack, value is in bytes. Same as discard. Typo. I meant Bytes. Your text is too long an too convoluted, so unclear. -- Damien Le Moal Western Digital Research
