Messages in this thread | | | Subject | Re: [PATCH] scsi: core: Cap shost cmd_per_lun at can_queue | From | Bart Van Assche <> | Date | Thu, 20 May 2021 09:57:35 -0700 |
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On 5/20/21 9:41 AM, John Garry wrote: > On 20/05/2021 16:57, Bart Van Assche wrote: >> In SCSI header files a mix of int, short and unsigned int is used for >> cmd_per_lun and can_queue. How about changing the types of these two >> member variables in include/scsi/*h into u16? > I don't mind doing that, but is there any requirement for can_queue to > not be limited to 16b?
Maybe I'm missing something but it is not clear to me why different structures in the SCSI headers use different data types for can_queue and cmd_per_lun?
$ git grep -nHEw '(cmd_per_lun|can_queue);' include/scsi include/scsi/scsi_device.h:318: unsigned int can_queue; include/scsi/scsi_host.h:372: int can_queue; include/scsi/scsi_host.h:425: short cmd_per_lun; include/scsi/scsi_host.h:612: int can_queue; include/scsi/scsi_host.h:613: short cmd_per_lun;
> It seems intentional that can_queue is int and cmd_per_lun is short.
Intentional? It is not clear to me why? Even high-performance drivers like iSER and SRP set can_queue by default to a value that fits well in a 16-bit variable (512 and 64 respectively). The highest value that I found after a quick search is the following:
#define ISCSI_TOTAL_CMDS_MAX 4096
Thanks,
Bart.
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