| Message ID | 20190214211759.699390983@linutronix.de (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | genirq/affinity: Overhaul the multiple interrupt sets support | expand |
On Thu, Feb 14, 2019 at 09:47:59PM +0100, Thomas Gleixner wrote: > From: Ming Lei <ming.lei@redhat.com> > > The NVME PCI driver contains a tedious mechanism for interrupt > allocation, which is necessary to adjust the number and size of interrupt > sets to the maximum available number of interrupts which depends on the > underlying PCI capabilities and the available CPU resources. > > It works around the former short comings of the PCI and core interrupt > allocation mechanims in combination with interrupt sets. > > The PCI interrupt allocation function allows to provide a maximum and a > minimum number of interrupts to be allocated and tries to allocate as > many as possible. This worked without driver interaction as long as there > was only a single set of interrupts to handle. > > With the addition of support for multiple interrupt sets in the generic > affinity spreading logic, which is invoked from the PCI interrupt > allocation, the adaptive loop in the PCI interrupt allocation did not > work for multiple interrupt sets. The reason is that depending on the > total number of interrupts which the PCI allocation adaptive loop tries > to allocate in each step, the number and the size of the interrupt sets > need to be adapted as well. Due to the way the interrupt sets support was > implemented there was no way for the PCI interrupt allocation code or the > core affinity spreading mechanism to invoke a driver specific function > for adapting the interrupt sets configuration. > > As a consequence the driver had to implement another adaptive loop around > the PCI interrupt allocation function and calling that with maximum and > minimum interrupts set to the same value. This ensured that the > allocation either succeeded or immediately failed without any attempt to > adjust the number of interrupts in the PCI code. > > The core code now allows drivers to provide a callback to recalculate the > number and the size of interrupt sets during PCI interrupt allocation, > which in turn allows the PCI interrupt allocation function to be called > in the same way as with a single set of interrupts. The PCI code handles > the adaptive loop and the interrupt affinity spreading mechanism invokes > the driver callback to adapt the interrupt set configuration to the > current loop value. This replaces the adaptive loop in the driver > completely. > > Implement the NVME specific callback which adjusts the interrupt sets > configuration and remove the adaptive allocation loop. > > [ tglx: Simplify the callback further and restore the dropped adjustment of > number of sets ] > > Signed-off-by: Ming Lei <ming.lei@redhat.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > --- > drivers/nvme/host/pci.c | 108 ++++++++++++------------------------------------ > 1 file changed, 28 insertions(+), 80 deletions(-) > > --- a/drivers/nvme/host/pci.c > +++ b/drivers/nvme/host/pci.c > @@ -2041,41 +2041,32 @@ static int nvme_setup_host_mem(struct nv > return ret; > } > > -/* irq_queues covers admin queue */ > -static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues) > +/* > + * nirqs is the number of interrupts available for write and read > + * queues. The core already reserved an interrupt for the admin queue. > + */ > +static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs) > { > - unsigned int this_w_queues = write_queues; > - > - WARN_ON(!irq_queues); > - > - /* > - * Setup read/write queue split, assign admin queue one independent > - * irq vector if irq_queues is > 1. > - */ > - if (irq_queues <= 2) { > - dev->io_queues[HCTX_TYPE_DEFAULT] = 1; > - dev->io_queues[HCTX_TYPE_READ] = 0; > - return; > - } > + struct nvme_dev *dev = affd->priv; > + unsigned int nr_read_queues; > > /* > - * If 'write_queues' is set, ensure it leaves room for at least > - * one read queue and one admin queue > - */ > - if (this_w_queues >= irq_queues) > - this_w_queues = irq_queues - 2; > - > - /* > - * If 'write_queues' is set to zero, reads and writes will share > - * a queue set. > - */ > - if (!this_w_queues) { > - dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues - 1; > - dev->io_queues[HCTX_TYPE_READ] = 0; > - } else { > - dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues; > - dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues - 1; > - } > + * If only one interrupt is available, combine write and read > + * queues. If 'write_queues' is set, ensure it leaves room for at > + * least one read queue. > + */ > + if (nrirqs == 1) > + nr_read_queues = 0; > + else if (write_queues >= nrirqs) > + nr_read_queues = nrirqs - 1; > + else > + nr_read_queues = nrirqs - write_queues; > + > + dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > + affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > + dev->io_queues[HCTX_TYPE_READ] = nr_read_queues; > + affd->set_size[HCTX_TYPE_READ] = nr_read_queues; > + affd->nr_sets = nr_read_queues ? 2 : 1; > } .calc_sets is called only if more than .pre_vectors is available, then dev->io_queues[HCTX_TYPE_DEFAULT] may not be set in case of (nvecs == affd->pre_vectors + affd->post_vectors). Thanks, Ming
On Fri, 15 Feb 2019, Ming Lei wrote: > > + * If only one interrupt is available, combine write and read > > + * queues. If 'write_queues' is set, ensure it leaves room for at > > + * least one read queue. > > + */ > > + if (nrirqs == 1) > > + nr_read_queues = 0; > > + else if (write_queues >= nrirqs) > > + nr_read_queues = nrirqs - 1; > > + else > > + nr_read_queues = nrirqs - write_queues; > > + > > + dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > > + affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > > + dev->io_queues[HCTX_TYPE_READ] = nr_read_queues; > > + affd->set_size[HCTX_TYPE_READ] = nr_read_queues; > > + affd->nr_sets = nr_read_queues ? 2 : 1; > > } > > .calc_sets is called only if more than .pre_vectors is available, > then dev->io_queues[HCTX_TYPE_DEFAULT] may not be set in case of > (nvecs == affd->pre_vectors + affd->post_vectors). Hmm, good catch. The delta patch below should fix that, but I have to go through all the possible cases in pci_alloc_irq_vectors_affinity() once more with brain awake. Thanks, tglx 8<--------------------- --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -2092,6 +2092,10 @@ static int nvme_setup_irqs(struct nvme_d } dev->io_queues[HCTX_TYPE_POLL] = this_p_queues; + /* Initialize for the single interrupt case */ + dev->io_queues[HCTX_TYPE_DEFAULT] = 1; + dev->io_queues[HCTX_TYPE_READ] = 0; + return pci_alloc_irq_vectors_affinity(pdev, 1, irq_queues, PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd); }
On Thu, 14 Feb 2019 20:47:59 +0000, Thomas Gleixner <tglx@linutronix.de> wrote: > > From: Ming Lei <ming.lei@redhat.com> > > The NVME PCI driver contains a tedious mechanism for interrupt > allocation, which is necessary to adjust the number and size of interrupt > sets to the maximum available number of interrupts which depends on the > underlying PCI capabilities and the available CPU resources. > > It works around the former short comings of the PCI and core interrupt > allocation mechanims in combination with interrupt sets. > > The PCI interrupt allocation function allows to provide a maximum and a > minimum number of interrupts to be allocated and tries to allocate as > many as possible. This worked without driver interaction as long as there > was only a single set of interrupts to handle. > > With the addition of support for multiple interrupt sets in the generic > affinity spreading logic, which is invoked from the PCI interrupt > allocation, the adaptive loop in the PCI interrupt allocation did not > work for multiple interrupt sets. The reason is that depending on the > total number of interrupts which the PCI allocation adaptive loop tries > to allocate in each step, the number and the size of the interrupt sets > need to be adapted as well. Due to the way the interrupt sets support was > implemented there was no way for the PCI interrupt allocation code or the > core affinity spreading mechanism to invoke a driver specific function > for adapting the interrupt sets configuration. > > As a consequence the driver had to implement another adaptive loop around > the PCI interrupt allocation function and calling that with maximum and > minimum interrupts set to the same value. This ensured that the > allocation either succeeded or immediately failed without any attempt to > adjust the number of interrupts in the PCI code. > > The core code now allows drivers to provide a callback to recalculate the > number and the size of interrupt sets during PCI interrupt allocation, > which in turn allows the PCI interrupt allocation function to be called > in the same way as with a single set of interrupts. The PCI code handles > the adaptive loop and the interrupt affinity spreading mechanism invokes > the driver callback to adapt the interrupt set configuration to the > current loop value. This replaces the adaptive loop in the driver > completely. > > Implement the NVME specific callback which adjusts the interrupt sets > configuration and remove the adaptive allocation loop. > > [ tglx: Simplify the callback further and restore the dropped adjustment of > number of sets ] > > Signed-off-by: Ming Lei <ming.lei@redhat.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > --- > drivers/nvme/host/pci.c | 108 ++++++++++++------------------------------------ > 1 file changed, 28 insertions(+), 80 deletions(-) > > --- a/drivers/nvme/host/pci.c > +++ b/drivers/nvme/host/pci.c > @@ -2041,41 +2041,32 @@ static int nvme_setup_host_mem(struct nv > return ret; > } > > -/* irq_queues covers admin queue */ > -static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues) > +/* > + * nirqs is the number of interrupts available for write and read > + * queues. The core already reserved an interrupt for the admin queue. > + */ > +static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs) > { > - unsigned int this_w_queues = write_queues; > - > - WARN_ON(!irq_queues); > - > - /* > - * Setup read/write queue split, assign admin queue one independent > - * irq vector if irq_queues is > 1. > - */ > - if (irq_queues <= 2) { > - dev->io_queues[HCTX_TYPE_DEFAULT] = 1; > - dev->io_queues[HCTX_TYPE_READ] = 0; > - return; > - } > + struct nvme_dev *dev = affd->priv; > + unsigned int nr_read_queues; > > /* > - * If 'write_queues' is set, ensure it leaves room for at least > - * one read queue and one admin queue > - */ > - if (this_w_queues >= irq_queues) > - this_w_queues = irq_queues - 2; > - > - /* > - * If 'write_queues' is set to zero, reads and writes will share > - * a queue set. > - */ > - if (!this_w_queues) { > - dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues - 1; > - dev->io_queues[HCTX_TYPE_READ] = 0; > - } else { > - dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues; > - dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues - 1; > - } > + * If only one interrupt is available, combine write and read > + * queues. If 'write_queues' is set, ensure it leaves room for at > + * least one read queue. [Full disclaimer: I only have had two coffees this morning, and it is only at the fourth that my brain is able to kick in...] I don't know much about NVME, but I feel like there is a small disconnect between the code and the above comment, which says "leave room for at least one read queue"... > + */ > + if (nrirqs == 1) > + nr_read_queues = 0; > + else if (write_queues >= nrirqs) > + nr_read_queues = nrirqs - 1; ... while this seem to ensure that we carve out one write queue out of the irq set. It looks like a departure from the original code, which would set nr_read_queues to 1 in that particular case. Thanks, M.
On Fri, 15 Feb 2019, Marc Zyngier wrote: > On Thu, 14 Feb 2019 20:47:59 +0000, > Thomas Gleixner <tglx@linutronix.de> wrote: > > drivers/nvme/host/pci.c | 108 ++++++++++++------------------------------------ > > 1 file changed, 28 insertions(+), 80 deletions(-) > > > > --- a/drivers/nvme/host/pci.c > > +++ b/drivers/nvme/host/pci.c > > @@ -2041,41 +2041,32 @@ static int nvme_setup_host_mem(struct nv > > return ret; > > } > > > > -/* irq_queues covers admin queue */ > > -static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues) > > +/* > > + * nirqs is the number of interrupts available for write and read > > + * queues. The core already reserved an interrupt for the admin queue. > > + */ > > +static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs) > > { > > - unsigned int this_w_queues = write_queues; > > - > > - WARN_ON(!irq_queues); > > - > > - /* > > - * Setup read/write queue split, assign admin queue one independent > > - * irq vector if irq_queues is > 1. > > - */ > > - if (irq_queues <= 2) { > > - dev->io_queues[HCTX_TYPE_DEFAULT] = 1; > > - dev->io_queues[HCTX_TYPE_READ] = 0; > > - return; > > - } > > + struct nvme_dev *dev = affd->priv; > > + unsigned int nr_read_queues; > > > > /* > > - * If 'write_queues' is set, ensure it leaves room for at least > > - * one read queue and one admin queue > > - */ > > - if (this_w_queues >= irq_queues) > > - this_w_queues = irq_queues - 2; > > - > > - /* > > - * If 'write_queues' is set to zero, reads and writes will share > > - * a queue set. > > - */ > > - if (!this_w_queues) { > > - dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues - 1; > > - dev->io_queues[HCTX_TYPE_READ] = 0; > > - } else { > > - dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues; > > - dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues - 1; > > - } > > + * If only one interrupt is available, combine write and read > > + * queues. If 'write_queues' is set, ensure it leaves room for at > > + * least one read queue. > > [Full disclaimer: I only have had two coffees this morning, and it is > only at the fourth that my brain is able to kick in...] > > I don't know much about NVME, but I feel like there is a small > disconnect between the code and the above comment, which says "leave > room for at least one read queue"... > > > + */ > > + if (nrirqs == 1) > > + nr_read_queues = 0; > > + else if (write_queues >= nrirqs) > > + nr_read_queues = nrirqs - 1; > > ... while this seem to ensure that we carve out one write queue out of > the irq set. It looks like a departure from the original code, which > would set nr_read_queues to 1 in that particular case. Bah. right you are.
On Fri, 15 Feb 2019, Thomas Gleixner wrote: > On Fri, 15 Feb 2019, Marc Zyngier wrote: > > > + */ > > > + if (nrirqs == 1) > > > + nr_read_queues = 0; > > > + else if (write_queues >= nrirqs) > > > + nr_read_queues = nrirqs - 1; > > > > ... while this seem to ensure that we carve out one write queue out of > > the irq set. It looks like a departure from the original code, which > > would set nr_read_queues to 1 in that particular case. > > Bah. right you are. That needs to be: nr_read_queues = 1; obviously. /me blushes.
On Fri, 15 Feb 2019, Thomas Gleixner wrote: > On Fri, 15 Feb 2019, Ming Lei wrote: > > > + * If only one interrupt is available, combine write and read > > > + * queues. If 'write_queues' is set, ensure it leaves room for at > > > + * least one read queue. > > > + */ > > > + if (nrirqs == 1) > > > + nr_read_queues = 0; > > > + else if (write_queues >= nrirqs) > > > + nr_read_queues = nrirqs - 1; > > > + else > > > + nr_read_queues = nrirqs - write_queues; > > > + > > > + dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > > > + affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; > > > + dev->io_queues[HCTX_TYPE_READ] = nr_read_queues; > > > + affd->set_size[HCTX_TYPE_READ] = nr_read_queues; > > > + affd->nr_sets = nr_read_queues ? 2 : 1; > > > } > > > > .calc_sets is called only if more than .pre_vectors is available, > > then dev->io_queues[HCTX_TYPE_DEFAULT] may not be set in case of > > (nvecs == affd->pre_vectors + affd->post_vectors). > > Hmm, good catch. The delta patch below should fix that, but I have to go > through all the possible cases in pci_alloc_irq_vectors_affinity() once > more with brain awake. The existing logic in the driver is somewhat strange. If there is only a single interrupt available, i.e. no separation of admin and I/O queue, then dev->io_queues[HCTX_TYPE_DEFAULT] is still set to 1. Now with the callback scheme (independent of my changes) that breaks in various ways: 1) irq_create_affinity_masks() bails out early: if (nvecs == affd->pre_vectors + affd->post_vectors) return NULL; So the callback won't be invoked and the last content of dev->io_queues is preserved. By chance this might end up with dev->io_queues[HCTX_TYPE_DEFAULT] = 1; dev->io_queues[HCTX_TYPE_READ] = 0; but that does not happen by design. 2) pci_alloc_irq_vectors_affinity() has the following flow: __pci_enable_msix_range() for (...) { __pci_enable_msix() } If that fails because MSIX is not supported, then the affinity spreading code has not been called yet and neither the callback. Now it goes on and tries MSI, which is the same as the above. When that fails because MSI is not supported, same situation as above and the code tries to allocate the legacy interrupt. Now with the initial initialization that case is covered, but not the following error case: Assume MSIX is enabled, but __pci_enable_msix() fails with -ENOMEM after having called irq_create_affinity_masks() and subsequently the callback with maxvecs. Then pci_alloc_irq_vectors_affinity() will try MSI and fail _BEFORE_ the callback is invoked. The next step is to install the leagcy interrupt, but that does not invoke the affinity code and neither the callback. At the end dev->io_queues[*] are still initialized with the failed attempt of enabling MSIX based on maxvecs. Result: inconsistent state ... I have an idea how to fix that, but that's again a task for brain being awake. Will take care of that tomorrow morning. Thanks, tglx
--- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -2041,41 +2041,32 @@ static int nvme_setup_host_mem(struct nv return ret; } -/* irq_queues covers admin queue */ -static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues) +/* + * nirqs is the number of interrupts available for write and read + * queues. The core already reserved an interrupt for the admin queue. + */ +static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs) { - unsigned int this_w_queues = write_queues; - - WARN_ON(!irq_queues); - - /* - * Setup read/write queue split, assign admin queue one independent - * irq vector if irq_queues is > 1. - */ - if (irq_queues <= 2) { - dev->io_queues[HCTX_TYPE_DEFAULT] = 1; - dev->io_queues[HCTX_TYPE_READ] = 0; - return; - } + struct nvme_dev *dev = affd->priv; + unsigned int nr_read_queues; /* - * If 'write_queues' is set, ensure it leaves room for at least - * one read queue and one admin queue - */ - if (this_w_queues >= irq_queues) - this_w_queues = irq_queues - 2; - - /* - * If 'write_queues' is set to zero, reads and writes will share - * a queue set. - */ - if (!this_w_queues) { - dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues - 1; - dev->io_queues[HCTX_TYPE_READ] = 0; - } else { - dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues; - dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues - 1; - } + * If only one interrupt is available, combine write and read + * queues. If 'write_queues' is set, ensure it leaves room for at + * least one read queue. + */ + if (nrirqs == 1) + nr_read_queues = 0; + else if (write_queues >= nrirqs) + nr_read_queues = nrirqs - 1; + else + nr_read_queues = nrirqs - write_queues; + + dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; + affd->set_size[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues; + dev->io_queues[HCTX_TYPE_READ] = nr_read_queues; + affd->set_size[HCTX_TYPE_READ] = nr_read_queues; + affd->nr_sets = nr_read_queues ? 2 : 1; } static int nvme_setup_irqs(struct nvme_dev *dev, unsigned int nr_io_queues) @@ -2083,10 +2074,9 @@ static int nvme_setup_irqs(struct nvme_d struct pci_dev *pdev = to_pci_dev(dev->dev); struct irq_affinity affd = { .pre_vectors = 1, - .nr_sets = 2, + .calc_sets = nvme_calc_irq_sets, + .priv = dev, }; - unsigned int *irq_sets = affd.set_size; - int result = 0; unsigned int irq_queues, this_p_queues; /* @@ -2102,51 +2092,8 @@ static int nvme_setup_irqs(struct nvme_d } dev->io_queues[HCTX_TYPE_POLL] = this_p_queues; - /* - * For irq sets, we have to ask for minvec == maxvec. This passes - * any reduction back to us, so we can adjust our queue counts and - * IRQ vector needs. - */ - do { - nvme_calc_io_queues(dev, irq_queues); - irq_sets[0] = dev->io_queues[HCTX_TYPE_DEFAULT]; - irq_sets[1] = dev->io_queues[HCTX_TYPE_READ]; - if (!irq_sets[1]) - affd.nr_sets = 1; - - /* - * If we got a failure and we're down to asking for just - * 1 + 1 queues, just ask for a single vector. We'll share - * that between the single IO queue and the admin queue. - * Otherwise, we assign one independent vector to admin queue. - */ - if (irq_queues > 1) - irq_queues = irq_sets[0] + irq_sets[1] + 1; - - result = pci_alloc_irq_vectors_affinity(pdev, irq_queues, - irq_queues, - PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd); - - /* - * Need to reduce our vec counts. If we get ENOSPC, the - * platform should support mulitple vecs, we just need - * to decrease our ask. If we get EINVAL, the platform - * likely does not. Back down to ask for just one vector. - */ - if (result == -ENOSPC) { - irq_queues--; - if (!irq_queues) - return result; - continue; - } else if (result == -EINVAL) { - irq_queues = 1; - continue; - } else if (result <= 0) - return -EIO; - break; - } while (1); - - return result; + return pci_alloc_irq_vectors_affinity(pdev, 1, irq_queues, + PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd); } static void nvme_disable_io_queues(struct nvme_dev *dev) @@ -3021,6 +2968,7 @@ static struct pci_driver nvme_driver = { static int __init nvme_init(void) { + BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS < 2); return pci_register_driver(&nvme_driver); }