在 2016/11/22 上午6:45, Robert LeBlanc 写道:
> I'm looking to improve 'near' layout performance in raid10 and looking
> at the code for read_balance, the comments mention that there is a
> 'next expected sequential IO' sector number stored for the RAID array,
> but I don't see such a variable in the struct, nor do I see in
> read_balance where that variable is being updated. With such a value,
> I could use it (with another variable) to guess if the current
> requests are random or sequential enough to take the latency hit to
> move drive heads to help parallel the read. This would be a much
> simpler route than what I was thinking about previously.
>
> Am I just missing this variable? I would expect it to be in the
> r10conf struct, would that be the right place to implement it if
> doesn't exist?
>
> Thanks,
> ----------------
> Robert LeBlanc
> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
Hi Robert,
This code was originally from Linux 2.6.9, it seems like copying from
raid1.c:read_balance(). IMHO you don't miss anything, we should remove
the following text from the comments,
There is a per-array 'next expected sequential IO' sector
number - if this matches on the next IO then we use the last disk.
How about compose a patch ?
Coly
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