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Usage of dm_delay looks to be slowing not just 'delayed' portion
of device, but due to the fact it's also slows down ANY flush
operation on such device it's overal speed impact is huge.
In some case we can however user other methods to slowdown disk writes,
in case of old dm 'mirror' target we can throttle I/O of mirror
synchronisation giving the next commands enough time to test couple
race conditions.
Usage:
throttle_dm_mirror [percentage]
Thtrottle down sync speed (lowest is '1' which is also default when
unspecified)
restore_dm_mirror
Restores the value of throttling before call of 'throttle_dm_mirror'
Usually it should '100'
Currently usage of loop device over backend file in ramdisk (tmpfs)
is actually causing unnecassary memory consution, since just
reading such loop device is causing RAM provisioning.
This patch add another possible way how to use ramdisk directly
through 'brd' device when possible (and allowed).
This however has it's limitation as well - brd does not support
TRIM, so the only way how to erase is to remove brd module ??
Alse there is 4K sector size limitation imposed by ramdisk.
Anyway - for some mirror test that were using large amount of
disk space (tens of MB) this brings noticable speed boost.
(But could be worth to solve the slowness of loop in kernel?)
To prevent using 'brd' for testing set LVM_TEST_PREFER_BRD=0
like this:
make check_local LVM_TEST_PREFER_BRD=0
This test can't use brd (ramdisk) as backend since for some
weird reason lsblk is not listing these device.
TODO: test could be probably rewritten to avoid using lsblk somehow??
When the backend device supports only 4K blocks (like ramdisk)
we cannot use for testing any smaller blocksize.
So recalc test for 4K extent size.
We may possibly introduce one list extra test that
can be executed on devices with 512b sectors to
check lvm2 support those min extent sizes...
An implementation of an adaptive radix tree. Has the following nice
properties:
- At least as fast as the hash table
- Uses less memory
- You don't need to give an expected size when you create
- It scales nicely (ie. no large reallocations like the hash table).
- You can iterate the keys in lexicographical order.
Only insert and lookup are implemented so far. Plus there's a lot
more performance to come.
In case "lvconvert -mN RaidLV" was used on a degraded
raid1 LV, success was returned instead of an error.
Provide message to inform about the need to repair first
before changing number of mirrors and exit with error.
Add new lvconvert-m-raid1-degraded.sh test.
Resolves: rhbz1573960
Put back a test like the old one that was removed
in d709d8445f206b67cfc06266ce7553f9cb6f3df5.
It verifies that lvm will ignore and not use a
gfs-pool device.
There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
When 'dmsetup' reports result with --nameprefixes it currently
incorrectly 'escapes' problematic characters.
Letting pass such string though shell 'eval' function is hard task.
So instead cut away substring.
Once dmsetup will start to properly escape backslash and apostrophe
this function may need further tuning.
Instead of using delayer device user 'zero' device and let mirror
do some real work which takes some time.
In case the test machine is too fast - mirror might need to be made bigger
to meet needed criteria.
Also move all test needed this 'zero' PV trick to the end of test
so $dev2 and $dev4 are covered with 'zero' and can take any amount of
write without consuming any real space.
For reporting commands (pvs,vgs,lvs,pvdisplay,vgdisplay,lvdisplay)
we do not need to repeat the label scan of devices in vg_read if
they all had matching metadata in the initial label scan. The
data read by label scan can just be reused for the vg_read.
This cuts the amount of device i/o in half, from two reads of
each device to one. We have to be careful to avoid repairing
the VG if we've skipped rescanning. (The VG repair code is very
poor, and will be redone soon.)
