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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...
ATM it's a bit ugly to enforce flushing of 'stdio' here, but works as quick
hot-fix.
log_print*() is using buffered I/O.
But for pooling with typical 1s interval this may take a while before
buffer about continues progress gets flushed.
So ATM fflush().
TODO: either add log_print*_with_flush() or maybe directly use just
line buffering with log_print() and only log_debug() keep using buffered
I/O mode.
md devices using an older superblock version have
superblocks at the end of the md device. For commands
that skip reading the end of devices during filtering,
the md component devs will be scanned, and will appear
as duplicate PVs to the original md device. Remove
these md components from the list of unused duplicate
devices, so they are treated as if they had been
ignored during filtering. This avoids the restrictions
that are placed on using PVs with duplicates.
All these functions are now used as utilities,
e.g. for ioctl (not for io), and need to
open/close the device each time they are called.
(Many of the opens can probably be eliminated by
just using the bcache fd for the ioctl.)
with the --labelsector option. We probably don't
need all this code to support any value for this
option; it's unclear how, when, why it would be
used.
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.
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
This reverts commit 0931067dc5.
The dep files should be in the build dir, which is not necc. the src dir.
Easy to fix, but reverting for now until I have time to revisit.
