lkml.org 
[lkml]   [2017]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v6 00/11] locking/rwsem: Rework rwsem-xadd & enable new rwsem features
From
Date
On 10/11/2017 04:50 PM, Dave Chinner wrote:
> On Wed, Oct 11, 2017 at 02:01:51PM -0400, Waiman Long wrote:
>> In term of rwsem performance, a rwsem microbenchmark and fio randrw
>> test with a xfs filesystem on a ramdisk were used to verify the
>> performance changes due to these patches. Both tests were run on a
>> 2-socket, 40-core Gold 6148 system. The rwsem microbenchmark (1:1
>> reader/writer ratio) has short critical section while the fio randrw
>> test has long critical section (4k read/write).
>>
>> The following table shows the performance of the rwsem microbenchmark
>> and fio radrw test with different number of patches applied on 4.14
>> based kernels:
>>
>> # of Patches Locking Rate FIO Bandwidth FIO Bandwidth
>> Applied 40 threads 32 threads 16 threads
>> ------------ ------------ ------------- -------------
>> 0 38.7 kop/s 706 MB/s 704 MB/s
>> 7 38.6 kop/s 668 MB/s 663 MB/s
>> 8 38.9 kop/s 704 MB/s 701 MB/s
>> 9 39.1 kop/s 702 MB/s 707 MB/s
>> 11 3218.0 kop/s 2594 MB/s 2614 MB/s
>>
>> So this patchset improves mixed read/write rwsem microbench by 83X
>> and randrw fio bandwidth by about 3.7X.
> Overall improvement in bandwidth is not necessarily a good thing -
> this could simply demonstrate total write bandwidth starvation and
> so it's only reporting read bandwith. It's much more important to
> look at the change in read bandwidth vs write bandwidth in the fio
> test. i.e. exactly how did the IO balance change as a result of
> changing the locking bias?

Thanks for the input. I can take out the reader lock stealing part. That
will give it a more fair reader/writer bias. It can also be an option
that be set when the rwsem is inited.

Cheers,
Longman


\
 
 \ /
  Last update: 2017-10-11 22:58    [W:0.124 / U:0.336 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site