Re: [ANNOUNCE][RELEASE]: megaraid unified driver version 2.20.0.B 1

[Jeff Garzik <jgarzik@pobox.com>]

Mukker, Atul wrote:
>>megaraid_clib.c:
>>  - why do you need the scb pool managment code at all?  You 
>>can dynamically
>>    allocate scbs in ->queuecommand
> 
> Will do. Please see the follow up question below

If there is a static maximum of scbs for megaraid hardware, dynamically 
allocating scbs in ->queuecommand is a waste of time.

In my drivers, I pre-allocate driver-specific per-request structures -- 
just like the SCSI layer does ;-)

If you follow this -- faster -- approach, make sure you don't waste a 
lot of memory with pre-allocated scb's you'll rarely use.


>>  - can you explain the need for all the mraid_pci_blk_pool?  
>>I.e. why the
>>    generic dma pool routines don't work for megaraid
> 
> We did not want to use pci_alloc_consistent because it would give one page
> even if we need 16 bytes (and we need a lot of these). Also, the
> pci_poo_create and pci_pool_alloc would fail on some setups - maybe because
> the driver requires lots of small chunks of DMAable buffers. So we decided
> to write wrapper functions over pci_alloc_consistent..

Would prefer to identify the root cause of pci_pool_xxx failure, since 
that is the proper API to use.

	Jeff