On Fri, Aug 4, 2023 at 9:33 AM Guo Ren <guoren@xxxxxxxxxx> wrote: > > On Thu, Aug 3, 2023 at 7:57 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > On Thu, Aug 03, 2023 at 06:28:51PM +0800, Guo Ren wrote: > > > On Thu, Aug 3, 2023 at 4:50 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > > > On Wed, Aug 02, 2023 at 07:14:05PM -0400, Guo Ren wrote: > > > > > > > > > The pv_ops is belongs to x86 custom frame work, and it prevent other > > > > > architectures connect to the CNA spinlock. > > > > > > > > static_call() exists as a arch neutral variant of this. > > > Emm... we have used static_call() in the riscv queued_spin_lock_: > > > https://lore.kernel.org/all/20230802164701.192791-20-guoren@xxxxxxxxxx/ > > > > Yeah, I think I saw that land in the INBOX, just haven't had time to > > look at it. > > > > > But we met a compile problem: > > > > > > GEN .vmlinux.objs > > > MODPOST Module.symvers > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [arch/riscv/kvm/kvm.ko] > > > undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" > > > [kernel/locking/locktorture.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [mm/z3fold.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" > > > [fs/nfs_common/grace.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [fs/quota/quota_v1.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [fs/quota/quota_v2.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" > > > [fs/quota/quota_tree.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [fs/fuse/virtiofs.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [fs/dlm/dlm.ko] undefined! > > > ERROR: modpost: "__SCK__pv_queued_spin_unlock" [fs/fscache/fscache.ko] > > > undefined! > > > WARNING: modpost: suppressed 839 unresolved symbol warnings because > > > there were too many) > > > /home/guoren/source/kernel/linux/scripts/Makefile.modpost:144: recipe > > > for target 'Module.symvers' failed > > > > > > Our solution is: > > > EXPORT_SYMBOL(__SCK__pv_queued_spin_unlock); > > > > > > What do you think about it? > > > > Could be you're not using static_call_mod() to go with > > EXPORT_STATIC_CALL_TRAMP() > Thx, that's what I want. > > > > > > > > I'm working on riscv qspinlock on sg2042 64 cores 2/4 NUMA nodes > > > > > platforms. Here are the patches about riscv CNA qspinlock: > > > > > https://lore.kernel.org/linux-riscv/20230802164701.192791-19-guoren@xxxxxxxxxx/ > > > > > > > > > > What's the next plan for this patch series? I think the two-queue design > > > > > has satisfied most platforms with two NUMA nodes. > > > > > > > > What has been your reason for working on CNA? What lock has been so > > > > contended you need this? > > > I wrote the reason here: > > > https://lore.kernel.org/all/20230802164701.192791-1-guoren@xxxxxxxxxx/ > > > > > > The target platform is: https://www.sophon.ai/ > > > > > > The two NUMA nodes platform has come out, so we want to measure the > > > benefit of CNA qspinlock. > > > > CNA should only show a benefit when there is strong inter-node > > contention, and in that case it is typically best to fix the kernel side > > locking. > > > > Hence the question as to what lock prompted you to look at this. > I met the long lock queue situation when the hardware gave an overly > aggressive store queue merge buffer delay mechanism. See: > https://lore.kernel.org/linux-riscv/20230802164701.192791-8-guoren@xxxxxxxxxx/ > > This also let me consider improving the efficiency of the long lock > queue release. For example, if the queue is like this: > > (Node0 cpu0) -> (Node1 cpu64) -> (Node0 cpu1) -> (Node1 cpu65) -> > (Node0 cpu2) -> (Node1 cpu66) -> ... > > Then every mcs_unlock would cause a cross-NUMA transaction. But if we > could make the queue like this: > > (Node0 cpu0) -> (Node0 cpu1) -> (Node0 cpu2) -> (Node1 cpu65) -> > (Node1 cpu66) -> (Node1 cpu64) -> ... > > Only one cross-NUMA transaction is needed. Although it would cause > starvation problems, qspinlock.numa_spinlock_threshold_ns could give a > basic guarantee. I thought it was a tradeoff for the balance between fairness and efficiency. > > -- > Best Regards > Guo Ren -- Best Regards Guo Ren
