linux-kernel - Re: [PATCH v5 00/18] locking/rwsem: Rwsem rearchitecture part 2

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Message-ID: <20190419124944.GA44010@gmail.com>
Date:   Fri, 19 Apr 2019 14:49:44 +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>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, 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>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH v5 00/18] locking/rwsem: Rwsem rearchitecture part 2


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Waiman Long <longman@...hat.com> wrote:
> 
> > On 04/18/2019 07:46 PM, Waiman Long wrote:
> > >  v5:
> > >   - Drop v4 patch 1 as it is merged into tip's locking/core branch.
> > >   - Integrate the 2 followup patches into the series. The first
> > >     follow-up patch is broken into 2 pieces. The first piece comes in
> > >     before the "Enable readers spinning on writer" and the 2nd piece
> > >     is merged into the "Enable time-based spinning on reader-owned
> > >     rwsem" patch. The 2nd followup patch is added after that.
> > >   - Add a new patch to make all wake_up_q() calls after dropping
> > >     wait_lock as suggested by PeterZ.
> > >   - Incorporate numerouos suggestions by PeterZ and Davidlohr.
> > 
> > This patchset is still being reviewed by Peter . The purpose of this
> > series is mainly to sync up the version that Peter has and the ones that
> > I am working on incorporating his feedback. Further changes may still be
> > needed.
> > 
> > I run an overall performance test on this new patchset and present the
> > data in this cover letter. However, I haven't run performance tests for
> > individual patches. So the performance data listed in some of the
> > patches may be stale.
> 
> Just for those who'd like to follow the scope of changes, find below the 
> v4->v5 interdiff. v5 is now included in tip:WIP.locking/core, and also 
> merged into tip:master. (But not propagated towards linux-next yet.)

Hm, I'm experiencing early boot hangs with v5, on defconfig-ish x86-64 
kernels:

[    0.153940] rcu: Hierarchical RCU implementation.
[    0.154289] rcu: 	RCU restricting CPUs from NR_CPUS=128 to nr_cpu_ids=17.
[    0.154829] rcu: RCU calculated value of scheduler-enlistment delay is 100 jiffies.
[    0.155390] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=17


I bisected it back to the v5 version of this patch:

  2fd5f60fa4c3: locking/rwsem: Merge owner into count on x86-64

I'm moving -tip back to -v4 meanwhile.

Thanks,

	Ingo