pie: fix kernel-doc notation warning

Spell a struct member's name correctly to prevent a kernel-doc
warning.

pie.h:38: warning: Function parameter or member 'tupdate' not described in 'pie_params'

Fixes: b42a3d7c7cff ("pie: improve comments and commenting style")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Leslie Monis <lesliemonis@gmail.com>
Cc: "Mohit P. Tahiliani" <tahiliani@nitk.edu.in>
Cc: Gautam Ramakrishnan <gautamramk@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Link: https://lore.kernel.org/r/20230714045127.18752-9-rdunlap@infradead.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

pie: realign comment

Realign a comment after the change introduced by the
previous patch.

Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: remove pie_vars->accu_prob_overflows

The variable pie_vars->accu_prob is used as an accumulator for
probability values. Since probabilty values are scaled using the
MAX_PROB macro denoting (2^64 - 1), pie_vars->accu_prob is
likely to overflow as it is of type u64.

The variable pie_vars->accu_prob_overflows counts the number of
times the variable pie_vars->accu_prob overflows.

The MAX_PROB macro needs to be equal to at least (2^39 - 1) in
order to do precise calculations without any underflow. Thus
MAX_PROB can be reduced to (2^56 - 1) without affecting the
precision in calculations drastically. Doing so will eliminate
the need for the variable pie_vars->accu_prob_overflows as the
variable pie_vars->accu_prob will never overflow.

Removing the variable pie_vars->accu_prob_overflows also reduces
the size of the structure pie_vars to exactly 64 bytes.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: use term backlog instead of qlen

Remove ambiguity by using the term backlog instead of qlen when
representing the queue length in bytes.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: sched: add Flow Queue PIE packet scheduler

Principles:
- Packets are classified on flows.
- This is a Stochastic model (as we use a hash, several flows might
be hashed to the same slot)
- Each flow has a PIE managed queue.
- Flows are linked onto two (Round Robin) lists,
so that new flows have priority on old ones.
- For a given flow, packets are not reordered.
- Drops during enqueue only.
- ECN capability is off by default.
- ECN threshold (if ECN is enabled) is at 10% by default.
- Uses timestamps to calculate queue delay by default.

Usage:
tc qdisc ... fq_pie [ limit PACKETS ] [ flows NUMBER ]
[ target TIME ] [ tupdate TIME ]
[ alpha NUMBER ] [ beta NUMBER ]
[ quantum BYTES ] [ memory_limit BYTES ]
[ ecnprob PERCENTAGE ] [ [no]ecn ]
[ [no]bytemode ] [ [no_]dq_rate_estimator ]

defaults:
limit: 10240 packets, flows: 1024
target: 15 ms, tupdate: 15 ms (in jiffies)
alpha: 1/8, beta : 5/4
quantum: device MTU, memory_limit: 32 Mb
ecnprob: 10%, ecn: off
bytemode: off, dq_rate_estimator: off

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Sachin D. Patil <sdp.sachin@gmail.com>
Signed-off-by: V. Saicharan <vsaicharan1998@gmail.com>
Signed-off-by: Mohit Bhasi <mohitbhasi1998@gmail.com>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: sched: pie: export symbols to be reused by FQ-PIE

This patch makes the drop_early(), calculate_probability() and
pie_process_dequeue() functions generic enough to be used by
both PIE and FQ-PIE (to be added in a future commit). The major
change here is in the way the functions take in arguments. This
patch exports these functions and makes FQ-PIE dependent on
sch_pie.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: improve comments and commenting style

Improve the comments along with the commenting style used to
describe the members of the structures and their initial values
in the init functions.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: rearrange structure members and their initializations

Rearrange the members of the structure such that closely
referenced members appear together and/or fit in the same
cacheline. Also, change the order of their initializations to
match the order in which they appear in the structure.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: use u8 instead of bool in pie_vars

Linux best practice recommends using u8 for true/false values in
structures.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: rearrange macros in order of length

Rearrange macros in order of length and align the values to
improve readability.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

pie: use U64_MAX to denote (2^64 - 1)

Use the U64_MAX macro to denote the constant (2^64 - 1).

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: sched: pie: move common code to pie.h

This patch moves macros, structures and small functions common
to PIE and FQ-PIE (to be added in a future commit) from the file
net/sched/sch_pie.c to the header file include/net/pie.h.
All the moved functions are made inline.

Signed-off-by: Mohit P. Tahiliani <tahiliani@nitk.edu.in>
Signed-off-by: Leslie Monis <lesliemonis@gmail.com>
Signed-off-by: Gautam Ramakrishnan <gautamramk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>