lkml.org 
[lkml]   [2015]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] block: blk-merge: fast-clone bio when splitting rw bios
From
On Thu, Sep 17, 2015 at 11:55 PM, Jens Axboe <axboe@kernel.dk> wrote:
> On 09/17/2015 09:50 AM, Ming Lei wrote:
>>
>> On Thu, Sep 17, 2015 at 11:19 PM, Jens Axboe <axboe@kernel.dk> wrote:
>>>
>>> On 09/17/2015 09:13 AM, Ming Lei wrote:
>>>>
>>>>
>>>> biovecs has become immutable since v3.13, so it isn't necessary
>>>> to allocate biovecs for the new cloned bios, then we can save
>>>> one extra biovecs allocation/copy, and the allocation is often
>>>> not fixed-length and a bit more expensive.
>>>>
>>>> For example, if the 'max_sectors_kb' of null blk's queue is set
>>>> as 16(32 sectors) via sysfs just for making more splits, this patch
>>>> can increase throught about ~70% in the sequential read test over
>>>> null_blk(direct io, bs: 1M).
>>>
>>>
>>>
>>> I'd be curious how this compares to before we did the splitting, not
>>> exceeding the limits through bio_add_page() instead?
>>
>>
>> Let me show these test results:
>>
>>
>> ----------------------------------------------------------------------------------
>> kernel | throught
>>
>> ----------------------------------------------------------------------------------
>> 4.3.0-rc1-next-20150916 | bw=12227MB/s, iops=12227
>>
>> ----------------------------------------------------------------------------------
>> 4.3.0-rc1-next-20150916 with patch | bw=21011MB/s, iops=21011
>>
>> ----------------------------------------------------------------------------------
>> v4.2 |
>> bw=18959MB/s, iops=18958
>>
>> ----------------------------------------------------------------------------------
>>
>> So from the above, looks this patch is kind of fix for performance
>> regression
>> introduced by 54efd50bfd(block: make generic_make_request handle
>> arbitrarily sized bios), :-)
>
>
> So that's 1MB user IO, and 16KB device limit, correct? If that is the case,

Yes, exactly, just for showing 'improvement' from the patch by setting
the limit, ;-)

> then the results make sense. And looks like we're still ahead of the older
> bio_add_page() approach, which is what I mostly cared about. Thanks! I'll
> apply this for -rc2.
>
> --
> Jens Axboe
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/


\
 
 \ /
  Last update: 2015-09-17 18:21    [W:0.088 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site