Re: [PATCH 4/4] target/rd: T10-Dif: RAM disk is allocating more space than required.

[Quinn Tran <quinn.tran@qlogic.com>]

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Regards,
Quinn Tran




On 3/28/14 5:22 PM, "sagi grimberg" <sagig@mellanox.com> wrote:

>On 3/29/2014 2:05 AM, Quinn Tran wrote:
>> Ram disk is allocating 8x more space than required for diff data.
>> For large RAM disk test, there is small potential for memory
>> starvation.
>>
>> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
>> Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
>> ---
>>   drivers/target/target_core_rd.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/target/target_core_rd.c
>>b/drivers/target/target_core_rd.c
>> index 01dda0b..6df177a 100644
>> --- a/drivers/target/target_core_rd.c
>> +++ b/drivers/target/target_core_rd.c
>> @@ -253,7 +253,11 @@ static int rd_build_prot_space(struct rd_dev
>>*rd_dev, int prot_length)
>>      if (rd_dev->rd_flags & RDF_NULLIO)
>>              return 0;
>>
>> -    total_sg_needed = rd_dev->rd_page_count / prot_length;
>> +    /* prot_length=8byte dif data
>> +     * tot sg needed = rd_page_count * (PGSZ/512) * (prot_length/PGSZ) +
>>pad
>> +     * PGSZ canceled each other.
>> +     */
>> +    total_sg_needed = (rd_dev->rd_page_count * prot_length / 512) +1;
>
>You probably will want to use block_size instead of hard-coding 512.
>Other then that this makes sense.

QT> agreed

>
>>
>>      sg_tables = (total_sg_needed / max_sg_per_table) + 1;
>>
>


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