> Subject: Re: [PATCH 01/17] net/mana: add basic driver, build environment and > doc > > On Sun, 3 Jul 2022 07:56:18 +0000 > Long Li <lon...@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 > > > lon...@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://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.re > searchgate.net%2Ffigure%2FCosts-of-Simple-Spinlock-and-Distributed-Reader- > Writer-Spinlock-To-write-acquire- > the_fig1_244490342&data=05%7C01%7Clongli%40microsoft.com%7C51cc > 3d29340347b87b8508da5ddc06c0%7C72f988bf86f141af91ab2d7cd011db47%7 > C1%7C0%7C637925496841806674%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC > 4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C > %7C%7C&sdata=bWePngCuLBWN%2FFasdYpTuuCJW6Y8kX6WVTInLYvd1E > c%3D&reserved=0 > > 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.
Thank you for the pointer! I think this driver should use spinlocks. I'm sending v2 with this change. Long
