On Sat, 26 Nov 2022 19:59:15 +1000, Nicholas Piggin wrote:
> This replaces the generic queued spinlock code (like s390 does) with
> our own implementation. There is an extra shim patch 1a to get the
> series to apply.
>
> Generic PV qspinlock code is causing latency / starvation regressions on
> large systems that are resulting in hard lockups reported (mostly in
> pathoogical cases). The generic qspinlock code has a number of issues
> important for powerpc hardware and hypervisors that aren't easily solved
> without changing code that would impact other architectures. Follow
> s390's lead and implement our own for now.
>
> [...]
Applied to powerpc/next.
[00/17] powerpc/qspinlock: powerpc qspinlock implementation
https://git.kernel.org/powerpc/c/9f61521c7a284e799050cd2adacc9a611bd2b491
[01/17] powerpc/qspinlock: add mcs queueing for contended waiters
https://git.kernel.org/powerpc/c/84990b169557428c318df87b7836cd15f65b62dc
[02/17] powerpc/qspinlock: use a half-word store to unlock to avoid larx/stcx.
https://git.kernel.org/powerpc/c/4c93c2e4b9e8988511c06b9c042f23d4b8f593ad
[03/17] powerpc/qspinlock: convert atomic operations to assembly
https://git.kernel.org/powerpc/c/b3a73b7db2b6cb3b2e5bfda5518a0e92230ef673
[04/17] powerpc/qspinlock: allow new waiters to steal the lock before queueing
https://git.kernel.org/powerpc/c/6aa42f883c438ea132a28801bef3f86f3883d14c
[05/17] powerpc/qspinlock: theft prevention to control latency
https://git.kernel.org/powerpc/c/0944534ef4d5cf39c8133575524be0be3337dd62
[06/17] powerpc/qspinlock: store owner CPU in lock word
https://git.kernel.org/powerpc/c/e1a31e7fd7130628cfd229253da2b4630e7a809c
[07/17] powerpc/qspinlock: paravirt yield to lock owner
https://git.kernel.org/powerpc/c/085f03311bcede99550e08a1f7cad41bf758b460
[08/17] powerpc/qspinlock: implement option to yield to previous node
https://git.kernel.org/powerpc/c/bd48287b2cf4cd6e95576db3a94fd2a7cdf9832d
[09/17] powerpc/qspinlock: allow stealing when head of queue yields
https://git.kernel.org/powerpc/c/b4c3cdc1a698a2f6168768d0bed4bf062723722e
[10/17] powerpc/qspinlock: allow propagation of yield CPU down the queue
https://git.kernel.org/powerpc/c/28db61e207ea3890d286cff3141c1ce67346074d
[11/17] powerpc/qspinlock: add ability to prod new queue head CPU
https://git.kernel.org/powerpc/c/be742c573fdafcfa1752642ca1c7aaf08c258128
[12/17] powerpc/qspinlock: allow lock stealing in trylock and lock fastpath
https://git.kernel.org/powerpc/c/f61ab43cc1a6146d6eef7e0713a452c3677ad13e
[13/17] powerpc/qspinlock: use spin_begin/end API
https://git.kernel.org/powerpc/c/71c235027ce7940434acd3f553602ad8b5d36469
[14/17] powerpc/qspinlock: reduce remote node steal spins
https://git.kernel.org/powerpc/c/cc79701114154efe79663ba47d9e51aad2ed3c78
[15/17] powerpc/qspinlock: allow indefinite spinning on a preempted owner
https://git.kernel.org/powerpc/c/39dfc73596b48bb50cf7e4f3f54e38427dda5b4e
[16/17] powerpc/qspinlock: provide accounting and options for sleepy locks
https://git.kernel.org/powerpc/c/12b459a5ebf3308e718bc1dd48acb7c4cf7f1a75
[17/17] powerpc/qspinlock: add compile-time tuning adjustments
https://git.kernel.org/powerpc/c/0b2199841a7952d01a717b465df028b40b2cf3e9
cheers
