Minwoo Im <minwoo.im.dev@xxxxxxxxx> 于2019年6月25日周二 上午6:00写道：
>
> On 19-06-24 22:29:19, Weiping Zhang wrote:
> > Now nvme support three type hardware queues, read, poll and default,
> > this patch rename write_queues to read_queues to set the number of
> > read queues more explicitly. This patch alos is prepared for nvme
> > support WRR(weighted round robin) that we can get the number of
> > each queue type easily.
> >
> > Signed-off-by: Weiping Zhang <zhangweiping@xxxxxxxxxxxxxx>
>
> Hello, Weiping.
>
> Thanks for making this patch as a separated one. Actually I'd like to
> hear about if the origin purpose of this param can be changed or not.
>
> I can see a log from Jens when it gets added her:
> Commit 3b6592f70ad7("nvme: utilize two queue maps, one for reads and
> one for writes")
> It says:
> """
> NVMe does round-robin between queues by default, which means that
> sharing a queue map for both reads and writes can be problematic
> in terms of read servicing. It's much easier to flood the queue
> with writes and reduce the read servicing.
> """
>
> So, I'd like to hear what other people think about this patch :)
>
This patch does not change its original behavior, if we set read_queue
greater than 0, the read and write request will use different tagset map,
so they will use different hardware queue.
> Thanks,
>
> > ---
> > drivers/nvme/host/pci.c | 22 ++++++++++------------
> > 1 file changed, 10 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> > index 5d84241f0214..a3c9bb72d90e 100644
> > --- a/drivers/nvme/host/pci.c
> > +++ b/drivers/nvme/host/pci.c
> > @@ -68,10 +68,10 @@ static int io_queue_depth = 1024;
> > module_param_cb(io_queue_depth, &io_queue_depth_ops, &io_queue_depth, 0644);
> > MODULE_PARM_DESC(io_queue_depth, "set io queue depth, should >= 2");
> >
> > -static int write_queues;
> > -module_param(write_queues, int, 0644);
> > -MODULE_PARM_DESC(write_queues,
> > - "Number of queues to use for writes. If not set, reads and writes "
> > +static int read_queues;
> > +module_param(read_queues, int, 0644);
> > +MODULE_PARM_DESC(read_queues,
> > + "Number of queues to use for reads. If not set, reads and writes "
> > "will share a queue set.");
> >
> > static int poll_queues;
> > @@ -211,7 +211,7 @@ struct nvme_iod {
> >
> > static unsigned int max_io_queues(void)
> > {
> > - return num_possible_cpus() + write_queues + poll_queues;
> > + return num_possible_cpus() + read_queues + poll_queues;
> > }
> >
> > static unsigned int max_queue_count(void)
> > @@ -2021,18 +2021,16 @@ static void nvme_calc_irq_sets(struct irq_affinity *affd, unsigned int nrirqs)
> > * If only one interrupt is available or 'write_queue' == 0, combine
> > * write and read queues.
> > *
> > - * If 'write_queues' > 0, ensure it leaves room for at least one read
> > + * If 'read_queues' > 0, ensure it leaves room for at least one write
> > * queue.
> > */
> > - if (!nrirqs) {
> > + if (!nrirqs || nrirqs == 1) {
> > nrirqs = 1;
> > nr_read_queues = 0;
> > - } else if (nrirqs == 1 || !write_queues) {
> > - nr_read_queues = 0;
> > - } else if (write_queues >= nrirqs) {
> > - nr_read_queues = 1;
> > + } else if (read_queues >= nrirqs) {
> > + nr_read_queues = nrirqs - 1;
> > } else {
> > - nr_read_queues = nrirqs - write_queues;
> > + nr_read_queues = read_queues;
> > }
> >
> > dev->io_queues[HCTX_TYPE_DEFAULT] = nrirqs - nr_read_queues;
> > --
> > 2.14.1
> >
