On 9/15/18 10:35 PM, Kai Krakow wrote:
In the past (I think back in 4.9), Eric sent some interesting writeback
hinting patches which I still carry around rebasing them with every
kernel version. I'm not sure if everything is still okay with these
patches or if I missed something during rebase, but my system is stable
with these.
Background: These patches allow processes with low IO priority to bypass
the bcache and thus reduce write load on the SSD. This is useful for
maintenance and backup jobs. It also ensures that such jobs won't
dominate the bcache and increases the chance of keeping important data
in the bcache. OTOH, important and IO sensitive processes can be made to
always use the bcache even when sequential cutoff would normally read
directly from the backing device bypassing bcache.
I wonder if there's still activity around this? Eric seems to have been
very silent AFAIT.
Are there chances to get this upstream? I remember there was some
discussion around this. If someone is interested, I can keep these
patches rebased in a public repo - or maybe someone with more insight in
bcache offers to do that.
Any thoughts on this? I think, Eric made some valuable patches which
allow lowering wear on SSDs.
Hi Kai,
Last time when this series was discussed, I remember there was opinion
that the interface was complicated.
IMHO we can simplify the interface by only input class level number to
the sysfs interface, e.g.
echo 7 > /sys/block/bcache0/bcache/ioprio_bypass
echo 0 > /sys/block/bcache0/bcache/ioprio_writeback
From Eric's document, behavior of I/O class 1 and 3 are always same,
the only thing can be changed is for I/O class 2. I may handle it in
other following changes.
In general this series is OK to me, we just need to design a simpler
interface. I may add them into my for-test directory, to test and
understand how it works, and then improve it if necessary.
Thanks.
Coly Li
