linux-kernel - Re: [PATCH-tip v2 00/12] locking/rwsem: Rwsem rearchitecture part 2

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Date:   Wed, 10 Apr 2019 12:00:54 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH-tip v2 00/12] locking/rwsem: Rwsem rearchitecture part 2


* Waiman Long <longman@...hat.com> wrote:

>    # of Threads   Before Patch      After Patch
>    ------------   ------------      -----------
>         2            1,179             9,436
>         4            1,505             8,268
>         8              721             7,041
>        16              575             7,652
>        32               70             2,189
>        64               39               534
> 
> Waiman Long (12):
>   locking/rwsem: Implement a new locking scheme
>   locking/rwsem: Implement lock handoff to prevent lock starvation
>   locking/rwsem: Remove rwsem_wake() wakeup optimization
>   locking/rwsem: Make rwsem_spin_on_owner() return owner state
>   locking/rwsem: Ensure an RT task will not spin on reader
>   locking/rwsem: Wake up almost all readers in wait queue
>   locking/rwsem: Enable readers spinning on writer
>   locking/rwsem: Enable time-based spinning on reader-owned rwsem
>   locking/rwsem: Add more rwsem owner access helpers
>   locking/rwsem: Guard against making count negative
>   locking/rwsem: Merge owner into count on x86-64
>   locking/rwsem: Remove redundant computation of writer lock word
> 
>  kernel/locking/lock_events_list.h |   4 +
>  kernel/locking/rwsem-xadd.c       | 635 +++++++++++++++++++-----------
>  kernel/locking/rwsem.c            |   3 +-
>  kernel/locking/rwsem.h            | 290 +++++++++++---
>  4 files changed, 647 insertions(+), 285 deletions(-)

Looks very nice!

With both sets of patches applied they pass all x86 tests, but there's 
cross-build failures on powerpc32, sparc32 and UML:

   kernel/locking/rwsem.h:333:34: error: 'struct rw_semaphore' has no member named 'owner'

Could you please send a delta patch against tip:WIP.locking/core, which 
is the work-in-progress tree? I'll backmerge the delta patch (and any 
other updates you might have meanwhil) to the one that introduces the 
breakage.

Thanks,

	Ingo