Re: Minutes from 10/1 LSE Call

[Hanna Linder]

Ahh. I see the confusion. These are excerpts from two different speakers.
Notice the line of ===== separating speakers in the minutes. 
This part is from Steve Pratt's mm vs mainline comparisons:


> On Thursday 02 October 2003 22:10, Jeff Garzik wrote:
>> insecure wrote:
>> > That sounds reasonable, but today's RAM throughput is on the order
>> > of 1GB/s, not 100Mb/s. 'Out of L1' theory can't explain 100Mb/s ceiling
>> > it seems.
>> 
>> cp(1) data, at least, will never ever be in L1.  Copying data you need
>> to look at the ends of the pipeline -- hard drive throughput, PCI bus
>> bandwidth, FSB bandwidth, speed at which ext2/3 allocates blocks, and
>> similar things are likely bottlenecks.
> 
> Hmm.
> 

This part is from Mark Gross's Real Time Application issues discussion:


> On Wednesday 01 October 2003 22:19, Hanna Linder wrote:
>> We got about 100 mb/sec using the bonie benchmark for block io writes,
>> for writes we hit a ceiling around 100-120 mb/sec. Stopped scaling
>> after about 3 spindles.
>> 
>> Tried to focus on the block io part of it. Have not tried
>> direct or raw io yet.  With block IO we got about 133 mb/sec
>> doing a simple dd to dev/null from multiple spindles. This
>> was on the 2.6 test 3.
>> ....
>> Odirect on large block sizes has low cpu utilization ( 3-5% ).
>> However with buffered IO we can easily get to 100% cpu utilization.
>> If you look at the profile most of that is in the copy_to_user function.
> 
> So:
> * we hit a ceiling of ~133 Mb/s, no matter how many disks
> * CPU utilization is 100%, spent mostly in copy_to_user
> * RAM bandwidth is >1Gb/s


Hanna

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