From: Jinpu Wang <jinpu.wang@cloud.ionos.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Jack Wang <jinpuwang@gmail.com>,
linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Sagi Grimberg <sagi@grimberg.me>,
Bart Van Assche <bvanassche@acm.org>,
Doug Ledford <dledford@redhat.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Danil Kipnis <danil.kipnis@cloud.ionos.com>,
Roman Penyaev <rpenyaev@suse.de>
Subject: Re: [PATCH v7 17/25] block/rnbd: client: main functionality
Date: Wed, 22 Jan 2020 12:22:43 +0100 [thread overview]
Message-ID: <CAMGffEkt1v+OkWOZfFBitYpqYHxB2+RHSjZbbLBZFPSuRXPMXQ@mail.gmail.com> (raw)
In-Reply-To: <20200120134815.GH51881@unreal>
> > +/**
> > + * rnbd_get_cpu_qlist() - finds a list with HW queues to be rerun
> > + * @sess: Session to find a queue for
> > + * @cpu: Cpu to start the search from
> > + *
> > + * Description:
> > + * Each CPU has a list of HW queues, which needs to be rerun. If a list
> > + * is not empty - it is marked with a bit. This function finds first
> > + * set bit in a bitmap and returns corresponding CPU list.
> > + */
> > +static struct rnbd_cpu_qlist *
> > +rnbd_get_cpu_qlist(struct rnbd_clt_session *sess, int cpu)
> > +{
> > + int bit;
> > +
> > + /* First half */
> > + bit = find_next_bit(sess->cpu_queues_bm, nr_cpu_ids, cpu);
>
> Is it protected by any lock?
We hold requeue_lock when set/clear bit, and disable preemption via
get_cpu_ptr when find_next_bit.
even it fails to get latest bit, it just cause an rerun the queue.
>
> > + if (bit < nr_cpu_ids) {
> > + return per_cpu_ptr(sess->cpu_queues, bit);
> > + } else if (cpu != 0) {
> > + /* Second half */
> > + bit = find_next_bit(sess->cpu_queues_bm, cpu, 0);
> > + if (bit < cpu)
> > + return per_cpu_ptr(sess->cpu_queues, bit);
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > +static inline int nxt_cpu(int cpu)
> > +{
> > + return (cpu + 1) % nr_cpu_ids;
> > +}
> > +
> > +/**
> > + * rnbd_rerun_if_needed() - rerun next queue marked as stopped
> > + * @sess: Session to rerun a queue on
> > + *
> > + * Description:
> > + * Each CPU has it's own list of HW queues, which should be rerun.
> > + * Function finds such list with HW queues, takes a list lock, picks up
> > + * the first HW queue out of the list and requeues it.
> > + *
> > + * Return:
> > + * True if the queue was requeued, false otherwise.
> > + *
> > + * Context:
> > + * Does not matter.
> > + */
> > +static inline bool rnbd_rerun_if_needed(struct rnbd_clt_session *sess)
>
> No inline function in C files.
First time saw such request, there are so many inline functions in C
files across the tree
grep inline drivers/infiniband/core/*.c
drivers/infiniband/core/addr.c:static inline bool
ib_nl_is_good_ip_resp(const struct nlmsghdr *nlh)
drivers/infiniband/core/cma.c:static inline u8 cma_get_ip_ver(const
struct cma_hdr *hdr)
drivers/infiniband/core/cma.c:static inline void cma_set_ip_ver(struct
cma_hdr *hdr, u8 ip_ver)
drivers/infiniband/core/cma.c:static inline void release_mc(struct kref *kref)
drivers/infiniband/core/cma.c:static inline struct sockaddr
*cma_src_addr(struct rdma_id_private *id_priv)
drivers/infiniband/core/cma.c:static inline struct sockaddr
*cma_dst_addr(struct rdma_id_private *id_priv)
>
> > +{
> > + struct rnbd_queue *q = NULL;
> > + struct rnbd_cpu_qlist *cpu_q;
> > + unsigned long flags;
> > + int *cpup;
> > +
> > + /*
> > + * To keep fairness and not to let other queues starve we always
> > + * try to wake up someone else in round-robin manner. That of course
> > + * increases latency but queues always have a chance to be executed.
> > + */
> > + cpup = get_cpu_ptr(sess->cpu_rr);
> > + for (cpu_q = rnbd_get_cpu_qlist(sess, nxt_cpu(*cpup)); cpu_q;
> > + cpu_q = rnbd_get_cpu_qlist(sess, nxt_cpu(cpu_q->cpu))) {
> > + if (!spin_trylock_irqsave(&cpu_q->requeue_lock, flags))
> > + continue;
> > + if (likely(test_bit(cpu_q->cpu, sess->cpu_queues_bm))) {
>
> Success oriented approach please.
sorry, I don't quite get your point.
Thanks Leon for review.
next prev parent reply other threads:[~2020-01-22 11:22 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 12:58 [PATCH v7 00/25] RTRS (former IBTRS) RDMA Transport Library and RNBD (former IBNBD) RDMA Network Block Device Jack Wang
2020-01-16 12:58 ` [PATCH v7 01/25] sysfs: export sysfs_remove_file_self() Jack Wang
2020-01-16 12:58 ` [PATCH v7 02/25] RDMA/rtrs: public interface header to establish RDMA connections Jack Wang
2020-01-16 12:58 ` [PATCH v7 03/25] RDMA/rtrs: private headers with rtrs protocol structs and helpers Jack Wang
2020-01-16 12:58 ` [PATCH v7 04/25] RDMA/rtrs: core: lib functions shared between client and server modules Jack Wang
2020-01-19 14:48 ` Leon Romanovsky
2020-01-20 11:32 ` Jinpu Wang
2020-01-20 13:30 ` Leon Romanovsky
2020-01-20 14:08 ` Jinpu Wang
2020-01-16 12:58 ` [PATCH v7 05/25] RDMA/rtrs: client: private header with client structs and functions Jack Wang
2020-01-16 12:58 ` [PATCH v7 06/25] RDMA/rtrs: client: main functionality Jack Wang
2020-01-16 14:53 ` Leon Romanovsky
2020-01-16 15:43 ` Jinpu Wang
2020-01-16 15:53 ` Jason Gunthorpe
2020-01-16 16:48 ` Jinpu Wang
2020-01-16 15:58 ` Leon Romanovsky
2020-01-16 16:24 ` Jinpu Wang
2020-01-18 10:12 ` Leon Romanovsky
2020-01-20 11:24 ` Jinpu Wang
2020-01-16 12:58 ` [PATCH v7 07/25] RDMA/rtrs: client: statistics functions Jack Wang
2020-01-16 12:58 ` [PATCH v7 08/25] RDMA/rtrs: client: sysfs interface functions Jack Wang
2020-01-16 12:58 ` [PATCH v7 09/25] RDMA/rtrs: server: private header with server structs and functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 10/25] RDMA/rtrs: server: main functionality Jack Wang
2020-01-16 12:59 ` [PATCH v7 11/25] RDMA/rtrs: server: statistics functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 12/25] RDMA/rtrs: server: sysfs interface functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 13/25] RDMA/rtrs: include client and server modules into kernel compilation Jack Wang
2020-01-16 12:59 ` [PATCH v7 14/25] RDMA/rtrs: a bit of documentation Jack Wang
2020-01-16 12:59 ` [PATCH v7 15/25] block/rnbd: private headers with rnbd protocol structs and helpers Jack Wang
2020-01-16 12:59 ` [PATCH v7 16/25] block/rnbd: client: private header with client structs and functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 17/25] block/rnbd: client: main functionality Jack Wang
2020-01-20 13:48 ` Leon Romanovsky
2020-01-20 17:30 ` Jinpu Wang
2020-01-22 12:31 ` Leon Romanovsky
2020-01-22 12:52 ` Jinpu Wang
2020-01-22 11:22 ` Jinpu Wang [this message]
2020-01-22 12:25 ` Leon Romanovsky
2020-01-22 13:12 ` Jinpu Wang
2020-01-22 14:07 ` Leon Romanovsky
2020-01-22 14:18 ` Jinpu Wang
2020-01-16 12:59 ` [PATCH v7 18/25] block/rnbd: client: sysfs interface functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 19/25] block/rnbd: server: private header with server structs and functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 20/25] block/rnbd: server: main functionality Jack Wang
2020-01-16 12:59 ` [PATCH v7 21/25] block/rnbd: server: functionality for IO submission to file or block dev Jack Wang
2020-01-16 12:59 ` [PATCH v7 22/25] block/rnbd: server: sysfs interface functions Jack Wang
2020-01-16 12:59 ` [PATCH v7 23/25] block/rnbd: include client and server modules into kernel compilation Jack Wang
2020-01-16 14:40 ` Leon Romanovsky
2020-01-16 14:54 ` Jinpu Wang
2020-01-16 15:59 ` Leon Romanovsky
2020-01-16 16:53 ` Jinpu Wang
2020-01-16 12:59 ` [PATCH v7 24/25] block/rnbd: a bit of documentation Jack Wang
2020-01-16 12:59 ` [PATCH v7 25/25] MAINTAINERS: Add maintainers for RNBD/RTRS modules Jack Wang
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