Re: ZRAM & read_ahead_kb

[Christian Ehrhardt]

Hi Fred,
not really the wrong, but also not fully the right place.
As the name implies the list is more for discussions/announcements - but
you already have a very specific solution in mind.
So I'd recommend opening a but against the zram-config at
https://bugs.launchpad.net/ubuntu/+source/zram-config

OTOH if I remember correctly device specific readaheads are usually a
device specific udev rule, but I'd let that discussion better be part of
the discussion in the LP bug.

Also you actually might want to read-ahead if there is an efficiency bonus
in bulk uncompressing it.
And I'm not sure if it even uses "normal" page cache on this sort of
backing device.
So if you have any data to back up the need for it please add it to the bug.
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ZRAM & read_ahead_kb

[Fred Bauer]

Could I request a small change to zram-config?
The default setting for /sys/block/zramN/queue/read_ahead_kb seems to
be 128 on my system.
It should really be zero since there's no point in reading RAM ahead of time.

diff for bin/init-zram-swapping:
  for i in $(seq ${NRDEVICES}); do
DEVNUMBER=$((i - 1))
echo $mem > /sys/block/zram${DEVNUMBER}/disksize
+   echo "0" >  /sys/block/zram${DEVNUMBER}/queue/read_ahead_kb
mkswap /dev/zram${DEVNUMBER}
swapon -p 5 /dev/zram${DEVNUMBER}
  done


My apologies if I'm not in the right place.

-- 
Fred W. Bauer
fred.w.ba...@gmail.com

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