[dm-devel] [Lsf-pc] [LSF/MM TOPIC] a few storage topics
Jeff Moyer
jmoyer at redhat.com
Tue Jan 24 19:14:14 UTC 2012
Chris Mason <chris.mason at oracle.com> writes:
>> All three filesystems use the generic mpages code for reads, so they
>> all get the same (bad) I/O patterns. Looks like we need to fix this up
>> ASAP.
>
> Can you easily run btrfs through the same rig? We don't use mpages and
> I'm curious.
The readahead code was to blame, here. I wonder if we can change the
logic there to not break larger I/Os down into smaller sized ones.
Fengguang, doing a dd if=file of=/dev/null bs=1M results in 128K I/Os,
when 128KB is the read_ahead_kb value. Is there any heuristic you could
apply to not break larger I/Os up like this? Does that make sense?
Cheers,
Jeff
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