On 2021/04/12 8:34, Damien Le Moal wrote:
> On 2021/04/12 1:30, Max Gurtovoy wrote:
>> This will enable changing the virtual boundary of null blk devices. For
>> now, null blk devices didn't have any restriction on the scatter/gather
>> elements received from the block layer. Add a module parameter that will
>> control the virtual boundary. This will enable testing the efficiency of
>> the block layer bounce buffer in case a suitable application will send
>> discontiguous IO to the given device.
>>
>> Initial testing with patched FIO showed the following results (64 jobs,
>> 128 iodepth):
>> IO size READ (virt=false) READ (virt=true) Write (virt=false) Write (virt=true)
>> ---------- ------------------- ----------------- ------------------- -------------------
>> 1k 10.7M 8482k 10.8M 8471k
>> 2k 10.4M 8266k 10.4M 8271k
>> 4k 10.4M 8274k 10.3M 8226k
>> 8k 10.2M 8131k 9800k 7933k
>> 16k 9567k 7764k 8081k 6828k
>> 32k 8865k 7309k 5570k 5153k
>> 64k 7695k 6586k 2682k 2617k
>> 128k 5346k 5489k 1320k 1296k
>>
>> Signed-off-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx>
>> ---
>> drivers/block/null_blk/main.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
>> index d6c821d48090..9ca80e38f7e5 100644
>> --- a/drivers/block/null_blk/main.c
>> +++ b/drivers/block/null_blk/main.c
>> @@ -84,6 +84,10 @@ enum {
>> NULL_Q_MQ = 2,
>> };
>>
>> +static bool g_virt_boundary = false;
>> +module_param_named(virt_boundary, g_virt_boundary, bool, 0444);
>> +MODULE_PARM_DESC(virt_boundary, "Require a virtual boundary for the device. Default: False");
>> +
>> static int g_no_sched;
>> module_param_named(no_sched, g_no_sched, int, 0444);
>> MODULE_PARM_DESC(no_sched, "No io scheduler");
>> @@ -1880,6 +1884,9 @@ static int null_add_dev(struct nullb_device *dev)
>> BLK_DEF_MAX_SECTORS);
>> blk_queue_max_hw_sectors(nullb->q, dev->max_sectors);
>>
>> + if (g_virt_boundary)
>> + blk_queue_virt_boundary(nullb->q, PAGE_SIZE - 1);
>> +
>> null_config_discard(nullb);
>>
>> sprintf(nullb->disk_name, "nullb%d", nullb->index);
>>
>
> Looks good to me, but could you also add the configfs equivalent setting ?
Oops. Chaitanya already had pointed this out... Sorry about the noise :)
--
Damien Le Moal
Western Digital Research
