lkml.org 
[lkml]   [2013]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: high-speed disk I/O is CPU-bound?
On 05/12/13 12:53, Rob Landley wrote:
> On 05/10/2013 09:04:44 AM, David Oostdyk wrote:
>> Hello,
>>
>> I have a few relatively high-end systems with hardware RAIDs which
>> are being used for recording systems, and I'm trying to get a better
>> understanding of contiguous write performance.
> ...
>> The question is, is it possible that high-speed I/O to these hardware
>> RAIDs could
>> actually be CPU-bound above ~1400MB/sec?
> In some setups your processor is calculating CRCs for the data. It's a
> fairly cheap operation, but a cheap operation on gigabytes of data can
> still saturate your memory bus.
>
> Rob

At what level would you say this calculation is being applied? Somewhere
in the block/filesystem layer, or in the device driver, or at the
hardware level? I'm seeing write speeds that are about 1/4 the memory
bandwidth of a single thread, which would suggest at least one
"additional" pass through the data before it gets DMA'd out.





\
 
 \ /
  Last update: 2013-05-13 18:01    [W:0.162 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site