kernel/linux.git/include/net/gen_stats.h, branch v6.12.80

net: sched: Remove Qdisc::running sequence counter

2021-10-18T11:54:41+00:00

The Qdisc::running sequence counter has two uses: 1. Reliably reading qdisc's tc statistics while the qdisc is running (a seqcount read/retry loop at gnet_stats_add_basic()). 2. As a flag, indicating whether the qdisc in question is running (without any retry loops). For the first usage, the Qdisc::running sequence counter write section, qdisc_run_begin() => qdisc_run_end(), covers a much wider area than what is actually needed: the raw qdisc's bstats update. A u64_stats sync point was thus introduced (in previous commits) inside the bstats structure itself. A local u64_stats write section is then started and stopped for the bstats updates. Use that u64_stats sync point mechanism for the bstats read/retry loop at gnet_stats_add_basic(). For the second qdisc->running usage, a __QDISC_STATE_RUNNING bit flag, accessed with atomic bitops, is sufficient. Using a bit flag instead of a sequence counter at qdisc_run_begin/end() and qdisc_is_running() leads to the SMP barriers implicitly added through raw_read_seqcount() and write_seqcount_begin/end() getting removed. All call sites have been surveyed though, and no required ordering was identified. Now that the qdisc->running sequence counter is no longer used, remove it. Note, using u64_stats implies no sequence counter protection for 64-bit architectures. This can lead to the qdisc tc statistics "packets" vs. "bytes" values getting out of sync on rare occasions. The individual values will still be valid. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Merge Qdisc::bstats and Qdisc::cpu_bstats data types

2021-10-18T11:54:41+00:00

The only factor differentiating per-CPU bstats data type (struct gnet_stats_basic_cpu) from the packed non-per-CPU one (struct gnet_stats_basic_packed) was a u64_stats sync point inside the former. The two data types are now equivalent: earlier commits added a u64_stats sync point to the latter. Combine both data types into "struct gnet_stats_basic_sync". This eliminates redundancy and simplifies the bstats read/write APIs. Use u64_stats_t for bstats "packets" and "bytes" data types. On 64-bit architectures, u64_stats sync points do not use sequence counter protection. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Protect Qdisc::bstats with u64_stats

2021-10-18T11:54:41+00:00

The not-per-CPU variant of qdisc tc (traffic control) statistics, Qdisc::gnet_stats_basic_packed bstats, is protected with Qdisc::running sequence counter. This sequence counter is used for reliably protecting bstats reads from parallel writes. Meanwhile, the seqcount's write section covers a much wider area than bstats update: qdisc_run_begin() => qdisc_run_end(). That read/write section asymmetry can lead to needless retries of the read section. To prepare for removing the Qdisc::running sequence counter altogether, introduce a u64_stats sync point inside bstats instead. Modify _bstats_update() to start/end the bstats u64_stats write section. For bisectability, and finer commits granularity, the bstats read section is still protected with a Qdisc::running read/retry loop and qdisc_run_begin/end() still starts/ends that seqcount write section. Once all call sites are modified to use _bstats_update(), the Qdisc::running seqcount will be removed and bstats read/retry loop will be modified to utilize the internal u64_stats sync point. Note, using u64_stats implies no sequence counter protection for 64-bit architectures. This can lead to the statistics "packets" vs. "bytes" values getting out of sync on rare occasions. The individual values will still be valid. [bigeasy: Minor commit message edits, init all gnet_stats_basic_packed.] Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

gen_stats: Move remaining users to gnet_stats_add_queue().

2021-10-18T11:54:41+00:00

The gnet_stats_queue::qlen member is only used in the SMP-case. qdisc_qstats_qlen_backlog() needs to add qdisc_qlen() to qstats.qlen to have the same value as that provided by qdisc_qlen_sum(). gnet_stats_copy_queue() needs to overwritte the resulting qstats.qlen field whith the caller submitted qlen value. It might be differ from the submitted value. Let both functions use gnet_stats_add_queue() and remove unused __gnet_stats_copy_queue(). Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

gen_stats: Add gnet_stats_add_queue().

2021-10-18T11:54:41+00:00

This function will replace __gnet_stats_copy_queue(). It reads all arguments and adds them into the passed gnet_stats_queue argument. In contrast to __gnet_stats_copy_queue() it also copies the qlen member. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

gen_stats: Add instead Set the value in __gnet_stats_copy_basic().

2021-10-18T11:54:40+00:00

__gnet_stats_copy_basic() always assigns the value to the bstats argument overwriting the previous value. The later added per-CPU version always accumulated the values in the returning gnet_stats_basic_packed argument. Based on review there are five users of that function as of today: - est_fetch_counters(), ___gnet_stats_copy_basic() memsets() bstats to zero, single invocation. - mq_dump(), mqprio_dump(), mqprio_dump_class_stats() memsets() bstats to zero, multiple invocation but does not use the function due to !qdisc_is_percpu_stats(). Add the values in __gnet_stats_copy_basic() instead overwriting. Rename the function to gnet_stats_add_basic() to make it more obvious. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net_sched: extend packet counter to 64bit

2019-11-06T02:20:55+00:00

After this change, qdisc packet counter is no longer a 32bit quantity. We still export 32bit values to user. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net_sched: do not export gnet_stats_basic_packed to uapi

2019-11-06T02:20:55+00:00

gnet_stats_basic_packed was really meant to be private kernel structure. If this proves to be a problem, we will have to rename the in-kernel version. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net: align gnet_stats_basic_cpu struct

2018-11-18T05:37:29+00:00

This structure is small (12 or 16 bytes depending on 64bit or 32bit kernels), but we do not want it spanning two cache lines. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net/core: Add new basic hardware counter

2018-09-24T19:18:42+00:00

Add a new hardware specific basic counter, TCA_STATS_BASIC_HW. This can be used to count packets/bytes processed by hardware offload. Signed-off-by: Eelco Chaudron Signed-off-by: David S. Miller