When limiting I/O, a value of 0 makes no sense as a limit. No progress
can be made. Trade the possibility that someone might be doing
something clever to achieve ultra-low I/O limits vs the damage of not
ever making progress on an I/O in favor of making progress. Now the
machine won't be useless if this accidentally gets requested.
Sponsored by: Netflix
Prevent cam_iosched_iops_tick() from discarding 'unspent' ios unless
it's a new accounting interval.
Previously ios that weren't used between ticks were lost, as a result
the iops limiter could enforce a limit below the configured maximum.
Obtained from: ElectroBSD
Submitted by: Fabian Keil
PR: 221974
Previously the iops limiter would always allow at least
quanta ios per second as cam_iosched_iops_tick() never set
ios->l_value1 below 1.
Submitted by: Fabian Keil <fk@fabiankeil.de>
Obtained from: ElectroBSD
PR: 221974
Previously ios->current was set to 0 until the first
cam_iosched_cl_maybe_steer() call.
PR: 221954
Obtained from: ElectroBSD
Submitted by: Fabian Keil
Differential Revision: https://reviews.freebsd.org/D12349
Previously callout_reset() was called with a "ticks" value that was
off by one. As a result cam_iosched_ticker() was called a bit too
frequently: On systems with hz=1000 a quanta value of 200 resulted in
~250 calls and a value of 100 in ~111 calls.
For the "queue_depth" and "bandwidth" limiters the difference doesn't
matter but the "iops" limiter depends on the scheduling to enforce the
correct maximum.
PR: 221956
Obtained from: ElectroBSD
Submitted by: Fabian Keil
Differential Revision: https://reviews.freebsd.org/D12350
Invalid values can result in devision-by-zero panics or other
undefined behaviour so lets not allow them.
PR: 221957
Obtained from: ElectroBSD
Submitted by: Fabian Keil
Differential Revision: https://reviews.freebsd.org/D12351
Use the write queue for BIO_ZONE commands so they can't get executed
ahead of writes that were sent after them. More generally, since they
introduce strong ordering into the list, they need to go to the write
queue (which is the only queue that BIO_ORDERED is honored for at the
moment). In fact, fix mismatch between queueing and dequeueing code by
changing this to queue all non-reads (and non-trims) to the write
queue.
As a side effect this prevents the kernel message:
kernel: Found bio_cmd = 0x9
which cam_iosched_next_bio() emits when finding commands
other than BIO_READ in the read queue.
PR: 221973
Obtained from: ElectroBSD
Submitted by: Fabian Keil
Differential Revision: https://reviews.freebsd.org/D12353
It's intended only for those situations where the periph driver
ones to limit the number of trims active to one and only one.
Also update comments on associated functions.
Sponsored by: Netflix
The cam_iosched_ticker() can't be scheduled more than once per tick.
Some limiters depend on quanta matching the number of calls per second
to enforce the proper limits. Limit the quanta to no faster than 1 per
clock tick. This fixes some features when running in VMs where the
default HZ is 100.
PR: 221953
Obtained from: ElectroBSD
Differential Revision: https://reviews.freebsd.org/D12337
Submitted by: Fabian Keil
extreme outliers from dodgy drives. Adjust comments to reflect this,
and make sure that the number of latency buckets match in the two
places where it matters.
o Allow I/O scheduler to gather times on 32-bit systems. We do this by shifting
the sbintime_t over by 8 bits and truncating to 32-bits. This gives us 8.24
time. This is sufficient both in range (256 seconds is about 128x what current
users need) and precision (60ns easily meets the 1ms smallest bucket size
measurements). 64-bit systems are unchanged. Centralize all the time math so
it's easy to tweak tha range / precision tradeoffs in the future.
o While I'm here, the I/O scheduler should be using periph_data rather than
sim_data since it is operating on behalf of the periph.
Differential Review: https://reviews.freebsd.org/D12119
we have queued up normaliazed to the queue size. Also compute buckets
of latency to help compute, in userland, estimates of Median, P90, P95
and P99 values.
Sponsored by: Netflix, Inc
