linux-kernel - Re: [PATCH v3 0/5] Add NUMA-awareness to qspinlock

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Message-Id: <1563277166.m9swqogbqb.astroid@bobo.none>
Date:   Tue, 16 Jul 2019 21:47:27 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Alex Kogan <alex.kogan@...cle.com>, arnd@...db.de, bp@...en8.de,
        guohanjun@...wei.com, hpa@...or.com, jglauber@...vell.com,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux@...linux.org.uk, linux-kernel@...r.kernel.org,
        longman@...hat.com, mingo@...hat.com, peterz@...radead.org,
        tglx@...utronix.de, will.deacon@....com, x86@...nel.org
Cc:     daniel.m.jordan@...cle.com, dave.dice@...cle.com,
        rahul.x.yadav@...cle.com, steven.sistare@...cle.com
Subject: Re: [PATCH v3 0/5] Add NUMA-awareness to qspinlock

Alex Kogan's on July 16, 2019 5:25 am:
> Our evaluation shows that CNA also improves performance of user 
> applications that have hot pthread mutexes. Those mutexes are 
> blocking, and waiting threads park and unpark via the futex 
> mechanism in the kernel. Given that kernel futex chains, which
> are hashed by the mutex address, are each protected by a 
> chain-specific spin lock, the contention on a user-mode mutex 
> translates into contention on a kernel level spinlock. 

What applications are those, what performance numbers? Arguably that's
much more interesting than microbenchmarks (which are mainly useful to
help ensure the fast paths are not impacted IMO).

Thanks,
Nick