Re: Ang: Re: [Stgt-devel] Re: [Iscsitarget-devel] stgt a new version of iscsi target?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Vladislav Bolkhovitin wrote:
Mike Christie wrote:

Dave C Boutcher wrote:

On Thu, Dec 08, 2005 at 02:09:32PM -0600, Mike Christie wrote:

James Bottomley wrote:

On Thu, 2005-12-08 at 13:10 -0600, Mike Christie wrote:


cleanup. In the end some of the scsi people liked the idea of throwing the non-read/write command to userspace and to do this we just decided to start over but I have been cutting and pasting your code and cleaning it up as I add more stuff.




To be honest, I'd like to see all command processing at user level
(including read/write ... for block devices, it shouldn't be that
inefficient, since you're merely going to say remap an area from one
device to another; as long as no data transformation ever occurs, the
user never touches the data and it all remains in the kernel page
cache).



Ok, Tomo and I briefly talked about this when we saw Jeff's post about doing block layer drivers in userspace on lkml. I think we were somewhat prepared for this given some of your other replies.

So Vlad and other target guys what do you think? Vlad are you going to continue to maintain scst as kernel only, or is there some place we can work together on this on - if your feelings are not hurt too much that is :) ?




Oofff....Architecturally I agree with James...do all command processing
in one place.  On the other hand, the processing involved with a read or
write in the normal case (no aborts/resets/ordering/timeouts/etc) is
almost zero.  Figure out the LBA and length and pass on the I/O.  The



There is still memory and scatterlist allocations. If we are not going to allocate all the memory for a command buffer and request with GFP_ATOMIC (and can then run from the the HW interrupt or soft irq) we have to pass that on to a thread. I guess there is disagreement whether that part is a feature or bad use of GFP_ATOMIC though so... But I just mean to say there could be a little more to do.


Actually, there is the way to allocate sg vectors with buffers in SIRQ and not with GFP_ATOMIC. This is the second major improvement, which is pending in scst. I called it sgv_pool. This is a new allocator in the kernel similar to mem_pool, but it contains *complete* sg-vectors of some size with data buffers (pages). Initiator sends data requests usually with some fixed size, like 128K. After a data command completed, its sg vector will not be immediately freed, but will be kept in

We considered this, but what did you decide is the upper limit size for the pool? Is it dynmaic? We also wanted something that the SCSI ULDs could use for their allocations which could go up to 6 MB.
-
: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Samba]     [Device Mapper]
  Powered by Linux