[clug] Kernel without initramfs

[Robert Edwards]

Daniel Pittman wrote:
...
> 
> (See the article for details of the operations, but the dataset is a
>  regular Linux kernel git repository and source tree.)
> 
> Amount of data written (in megabytes) on an ext4 filesystem
> Operation	with journal	w/o journal	percent change
> git clone	367.7           353.0           4.00%
> make            231.1           203.4           12.0%
> make clean	14.6            7.7             47.3%
> 
> Amount of data written (in megabytes) on an ext4 filesystem
>     mounted with noatime
> Operation	with journal	w/o journal	percent change
> git clone	367.0	        353.0	        3.81%
> make	        207.6	        199.4	        3.95%
> make clean	6.45	        3.73	        42.17%
> 
> 
> Metadata heavy workloads — delete a lot of stuff, specifically, which
> *really* sucks on ext3 in terms of I/O writes — might cost close to
> twice as much, but normal workloads are vastly better.
> 

I have been thinking a bit about these numbers and have come to the
conclusion that they don't really tell the whole picture in terms of
number of FLASH "blocks" being erased and re-written. My thinking goes
like: the actual writing of large chunks of data will generally be
whole-block writes, whereas the updating of the journal may be small
chucks of data, but still needs to be done per f/s change. So, although
the overall number of bytes being written to the journal may be small,
the number of FLASH blocks being erased and rewritten could still be
quite large.

But that is just my thinking - next is to come up with a way of
measuring what is actually happening at the FLASH chip layer (or, at
least, at the block layer).

Cheers,

Bob Edwards.