MFH: r280643-r281852

Sponsored by: The FreeBSD Foundation

Merge from HEAD

Fix overflow bugs in and remove obsolete limit from kernel RPC
implementation.

The kernel RPC code, which is responsible for the low-level scheduling
of incoming NFS requests, contains a throttling

Fix overflow bugs in and remove obsolete limit from kernel RPC
implementation.

The kernel RPC code, which is responsible for the low-level scheduling
of incoming NFS requests, contains a throttling mechanism that
prevents too much kernel memory from being tied up by NFS requests
that are being serviced. When the throttle is engaged, the RPC layer
stops servicing incoming NFS sockets, resulting ultimately in
backpressure on the clients (if they're using TCP). However, this is
a very heavy-handed mechanism as it prevents all clients from making
any requests, regardless of how heavy or light they are. (Thus, when
engaged, the throttle often prevents clients from even mounting the
filesystem.) The throttle mechanism applies specifically to requests
that have been received by the RPC layer (from a TCP or UDP socket)
and are queued waiting to be serviced by one of the nfsd threads; it
does not limit the amount of backlog in the socket buffers.

The original implementation limited the total bytes of queued requests
to the minimum of a quarter of (nmbclusters * MCLBYTES) and 45 MiB.
The former limit seems reasonable, since requests queued in the socket
buffers and replies being constructed to the requests in progress will
all require some amount of network memory, but the 45 MiB limit is
plainly ridiculous for modern memory sizes: when running 256 service
threads on a busy server, 45 MiB would result in just a single
maximum-sized NFS3PROC_WRITE queued per thread before throttling.

Removing this limit exposed integer-overflow bugs in the original
computation, and related bugs in the routines that actually account
for the amount of traffic enqueued for service threads. The old
implementation also attempted to reduce accounting overhead by
batching updates until each queue is fully drained, but this is prone
to livelock, resulting in repeated accumulate-throttle-drain cycles on
a busy server. Various data types are changed to long or unsigned
long; explicit 64-bit types are not used due to the unavailability of
64-bit atomics on many 32-bit platforms, but those platforms also
cannot support nmbclusters large enough to cause overflow.

This code (in a 10.1 kernel) is presently running on production NFS
servers at CSAIL.

Summary of this revision:
* Removes 45 MiB limit on requests queued for nfsd service threads
* Fixes integer-overflow and signedness bugs
* Avoids unnecessary throttling by not deferring accounting for
completed requests

Differential Revision: https://reviews.freebsd.org/D2165
Reviewed by: rmacklem, mav
MFC after: 30 days
Relnotes: yes
Sponsored by: MIT Computer Science & Artificial Intelligence Laboratory

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Reintegrate head: r274132-r277384

Sponsored by: The FreeBSD Foundation

Reintegrate head revisions r273096-r277147

Sponsored by: The FreeBSD Foundation

MFhead @ r275911 (also, sort out MK_* flags in BMAKE, etc on this branch)

Merge ^/head r275715 through r275748.

Add facility to stop all userspace processes. The supposed use of the
feature is to quisce the system before suspend.

Stop is implemented by reusing the thread_single(9) with the special
mode SINGL

Add facility to stop all userspace processes. The supposed use of the
feature is to quisce the system before suspend.

Stop is implemented by reusing the thread_single(9) with the special
mode SINGLE_ALLPROC. SINGLE_ALLPROC differs from the existing
single-threading modes by allowing (requiring) caller to operate on
other process. Interruptible sleeps for !TDF_SBDRY threads are
suspended like SIGSTOP does it, instead of aborting the sleep, like
SINGLE_NO_EXIT, to avoid spurious EINTRs on resume.

Provide debugging sysctl debug.stop_all_proc, which causes total stop
and suspends syncer, while waiting for variable reset for resume. It
is used for debugging; should be removed after the real use of the
interface is added.

In collaboration with: pho
Discussed with: avg
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks

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MFhead @ r275663

Merge ^/head r275478 through r275622.

Current reaction of the nfsd worker threads to any signal is exit.
This is not correct at least for the stop requests. Check for stop
conditions and suspend threads if requested.

Reported and teste

Current reaction of the nfsd worker threads to any signal is exit.
This is not correct at least for the stop requests. Check for stop
conditions and suspend threads if requested.

Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

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IFC @r269962

Submitted by: Anish Gupta (akgupt3@gmail.com)

Merge head from 7/28

Fix race in r267221.

MFC after: 2 weeks

Split RPC pool threads into number of smaller semi-isolated groups.

Old design with unified thread pool was good from the point of thread
utilization. But single pool-wide mutex became huge congest

Split RPC pool threads into number of smaller semi-isolated groups.

Old design with unified thread pool was good from the point of thread
utilization. But single pool-wide mutex became huge congestion point
for systems with many CPUs. To reduce the congestion create several
thread groups within a pool (one group for every 6 CPUs and 12 threads),
each group with own mutex. Each connection during its registration is
assigned to one of the groups in round-robin fashion. File affinify
code may still move requests between the groups, but otherwise groups
are self-contained.

MFC after: 2 weeks
Sponsored by: iXsystems, Inc.

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Remove st_idle variable, duplicating st_xprt.

MFC after: 2 weeks

Introduce new per-thread lock to protect the list of requests.

This allows to slightly simplify svc_run_internal() code: if we processed
all the requests in a queue, then we know that new one will n

Introduce new per-thread lock to protect the list of requests.

This allows to slightly simplify svc_run_internal() code: if we processed
all the requests in a queue, then we know that new one will not appear.

MFC after: 2 weeks

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MFC @ r266724

An SVM update will follow this.

Merge head

IFC @264767

MFH: tracking commit

Sponsored by: The FreeBSD Foundation

Merge head up to r262222 (last merge was incomplete).

MFC @ r259205 in preparation for some SVM updates. (for real this time)

Fix lock acquisition in case no request space available, missed in r260097.

MFC after: 3 days

MFH: tracking commit (head@r260486)

Sponsored by: The FreeBSD Foundation