From: Stephen Hemminger <stephen@networkplumber.org>
To: Long Li <longli@microsoft.com>
Cc: "longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
Ferruh Yigit <ferruh.yigit@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
Ajay Sharma <sharmaajay@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>
Subject: Re: [PATCH 01/17] net/mana: add basic driver, build environment and doc
Date: Mon, 4 Jul 2022 09:41:17 -0700 [thread overview]
Message-ID: <20220704094117.340d9b46@hermes.local> (raw)
In-Reply-To: <PH7PR21MB32633E0C874B43B85C15B5FDCEBF9@PH7PR21MB3263.namprd21.prod.outlook.com>
On Sun, 3 Jul 2022 07:56:18 +0000
Long Li <longli@microsoft.com> wrote:
> > Subject: Re: [PATCH 01/17] net/mana: add basic driver, build environment and
> > doc
> >
> > On Fri, 1 Jul 2022 02:02:31 -0700
> > longli@linuxonhyperv.com wrote:
> >
> > > + uint64_t max_mr_size;
> > > + rte_rwlock_t mr_list_lock;
> > > +};
> >
> > Reader/Writer locks are slower for the usual uncontended case.
> > Unless you have a reader holding onto the lock for a long time, better to use
> > spin lock.
> >
> > This is Linux wisdom (thank you paulmck), Windows seems to love reader/writer
> > locks.
>
> This lock is used mostly uncontended for readers and allow them concurrently to access the list. It's rare that a writer might want to access it.
>
> But changing it to spinlock will prevent multiple readers from accessing the list at the same time. In this use case, is it beneficial to use spinlocks?
https://www.researchgate.net/figure/Costs-of-Simple-Spinlock-and-Distributed-Reader-Writer-Spinlock-To-write-acquire-the_fig1_244490342
Conclusion
Breakeven curves for the locking primitives were
computed, and the breakeven between simple spinlock
and distributed reader-writer spinlock supports the rule of
thumb that states that simple spinlock should be used in
cases where the update ratio f is greater than the
reciprocal of the number of CPUs, 1/nm.
next prev parent reply other threads:[~2022-07-04 16:41 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-01 9:02 [PATCH 00/17] Introduce Microsoft Azure Network Adatper (MANA) PMD longli
2022-07-01 9:02 ` [PATCH 01/17] net/mana: add basic driver, build environment and doc longli
2022-07-01 16:29 ` Stephen Hemminger
2022-07-01 16:44 ` Stephen Hemminger
2022-07-01 16:45 ` Stephen Hemminger
2022-07-01 16:47 ` Stephen Hemminger
2022-07-03 7:56 ` Long Li
2022-07-04 16:35 ` Stephen Hemminger
2022-07-04 16:41 ` Stephen Hemminger [this message]
2022-07-05 19:50 ` Long Li
2022-07-01 16:49 ` Stephen Hemminger
2022-07-01 19:40 ` Long Li
2022-07-01 9:02 ` [PATCH 02/17] net/mana: add device configuration and stop longli
2022-07-01 16:34 ` Stephen Hemminger
2022-07-01 9:02 ` [PATCH 03/17] net/mana: add function to report support ptypes longli
2022-07-01 9:02 ` [PATCH 04/17] net/mana: add link update longli
2022-07-01 9:02 ` [PATCH 05/17] net/mana: add function for device removal interrupts longli
2022-07-01 9:02 ` [PATCH 06/17] net/mana: add device info longli
2022-07-01 9:02 ` [PATCH 07/17] net/mana: add function to configure RSS longli
2022-07-01 9:02 ` [PATCH 08/17] net/mana: add function to configure RX queues longli
2022-07-01 9:02 ` [PATCH 09/17] net/mana: add function to configure TX queues longli
2022-07-01 9:02 ` [PATCH 10/17] net/mana: implement memory registration longli
2022-07-01 16:37 ` Stephen Hemminger
2022-07-01 9:02 ` [PATCH 11/17] net/mana: implement the hardware layer operations longli
2022-07-01 16:38 ` Stephen Hemminger
2022-07-01 9:02 ` [PATCH 12/17] net/mana: add function to start/stop TX queues longli
2022-07-01 16:39 ` Stephen Hemminger
2022-07-01 9:02 ` [PATCH 13/17] net/mana: add function to start/stop RX queues longli
2022-07-01 16:40 ` Stephen Hemminger
2022-07-02 8:42 ` Long Li
2022-07-01 9:02 ` [PATCH 14/17] net/mana: add function to receive packets longli
2022-07-01 9:02 ` [PATCH 15/17] net/mana: add function to send packets longli
2022-07-01 9:02 ` [PATCH 16/17] net/mana: add function to start/stop device longli
2022-07-01 9:02 ` [PATCH 17/17] net/mana: add function to report queue stats longli
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