> From: Andrea Arcangeli [mailto:aarcange@xxxxxxxxxx]
> Sent: January 25, 2012 5:46 PM
....
> Way more important is to have feedback on the readahead hits and be
> sure when readahead is raised to the maximum the hit rate is near 100%
> and fallback to lower readaheads if we don't get that hit rate. But
> that's not a VM problem and it's a readahead issue only.
>
A quick google showed up - http://kerneltrap.org/node/6642
Interesting thread to follow. I haven't looked further as to what was
merged and what wasn't.
A quote from the patch - " It works by peeking into the file cache and
check if there are any history pages present or accessed."
Now I don't understand anything about this but I would think digging the
file-cache isn't needed(?). So, yes, a simple RA hit-rate feedback could
be fine.
And 'maybe' for adaptive RA just increase the RA-blocks by '1'(or some
N) over period of time. No more smartness. A simple 10 line function is
easy to debug/maintain. That is, a scaled-down version of
ramp-up/ramp-down. Don't go crazy by ramping-up/down after every RA(like
SCSI LLDD madness). Wait for some event to happen.
I can see where Andrew Morton's concerns could be(just my
interpretation). We may not want to end up like a protocol state machine
code: tcp slow-start, then increase , then congestion, then let's
back-off. hmmm, slow-start is a problem for my business logic, so let's
speed-up slow-start ;).
Chetan
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
[DM Crypt]
[Fedora Desktop]
[ATA RAID]
[Fedora Marketing]
[Fedora Packaging]
[Fedora SELinux]
[Yosemite Discussion]
[Yosemite Photos]
[KDE Users]
[Fedora Tools]
[Fedora Docs]
