LinuxPPC-Dev Archive on lore.kernel.org
 help / color / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: linux-arch <linux-arch@vger.kernel.org>,
	linux-xtensa@linux-xtensa.org,
	Davidlohr Bueso <dave@stgolabs.net>,
	linux-ia64@vger.kernel.org, Tim Chen <tim.c.chen@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-hexagon@vger.kernel.org,
	the arch/x86 maintainers <x86@kernel.org>,
	Will Deacon <will.deacon@arm.com>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-alpha@vger.kernel.org, sparclinux@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	linuxppc-dev@lists.ozlabs.org,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH-tip 00/22] locking/rwsem: Rework rwsem-xadd & enable new rwsem features
Date: Fri, 8 Feb 2019 11:50:40 -0800
Message-ID: <CAHk-=wjfyrFBjifzmgMVrkrvEePEPaBTDq7D=f2i5kD2E=SqRQ@mail.gmail.com> (raw)
In-Reply-To: <1549566446-27967-1-git-send-email-longman@redhat.com>

On Thu, Feb 7, 2019 at 11:08 AM Waiman Long <longman@redhat.com> wrote:
>
> This patchset revamps the current rwsem-xadd implementation to make
> it saner and easier to work with. This patchset removes all the
> architecture specific assembly code and uses generic C code for all
> architectures. This eases maintenance and enables us to enhance the
> code more easily.
>
> This patchset also implements the following 3 new features:
>
>  1) Waiter lock handoff
>  2) Reader optimistic spinning
>  3) Store write-lock owner in the atomic count (x86-64 only)

The patches are kind of hard to read, with most of them just doing
prep-work that doesn't necessarily matter to the big picture.

What I'd really like to see is

 (a) an overview of the new locking logic

 (b) what's the new fastpath case

 (c) some performance numbers

to explain the changes from a "this is the point of the whole
exercise" standpoint.

And yes, I realize that the lock handoff and optimistic spinning is a
big deal, since I've seen the same regression numbers that presumably
caused this effort to be resurrected. So it's not that I don't find
this intriguing and worthwhile, it's literally that I'd like a summary
not so much of the individual patches, but of the new model.

Please?

             Linus

  parent reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-07 19:07 Waiman Long
2019-02-07 19:07 ` [PATCH-tip 01/22] locking/qspinlock_stat: Introduce a generic lockevent counting APIs Waiman Long
2019-02-07 19:07 ` [PATCH-tip 02/22] locking/lock_events: Make lock_events available for all archs & other locks Waiman Long
2019-02-07 19:07 ` [PATCH-tip 03/22] locking/rwsem: Relocate rwsem_down_read_failed() Waiman Long
2019-02-07 19:07 ` [PATCH-tip 04/22] locking/rwsem: Remove arch specific rwsem files Waiman Long
2019-02-07 19:36   ` Peter Zijlstra
2019-02-07 19:43     ` Waiman Long
2019-02-07 19:48     ` Peter Zijlstra
2019-02-07 19:07 ` [PATCH-tip 05/22] locking/rwsem: Move owner setting code from rwsem.c to rwsem.h Waiman Long
2019-02-07 19:07 ` [PATCH-tip 06/22] locking/rwsem: Rename kernel/locking/rwsem.h Waiman Long
2019-02-07 19:07 ` [PATCH-tip 07/22] locking/rwsem: Move rwsem internal function declarations to rwsem-xadd.h Waiman Long
2019-02-07 19:07 ` [PATCH-tip 08/22] locking/rwsem: Add debug check for __down_read*() Waiman Long
2019-02-07 19:07 ` [PATCH-tip 09/22] locking/rwsem: Enhance DEBUG_RWSEMS_WARN_ON() macro Waiman Long
2019-02-07 19:07 ` [PATCH-tip 10/22] locking/rwsem: Enable lock event counting Waiman Long
2019-02-07 19:07 ` [PATCH-tip 11/22] locking/rwsem: Implement a new locking scheme Waiman Long
2019-02-07 19:07 ` [PATCH-tip 12/22] locking/rwsem: Implement lock handoff to prevent lock starvation Waiman Long
2019-02-07 19:07 ` [PATCH-tip 13/22] locking/rwsem: Remove rwsem_wake() wakeup optimization Waiman Long
2019-02-07 19:07 ` [PATCH-tip 14/22] locking/rwsem: Add more rwsem owner access helpers Waiman Long
2019-02-07 19:07 ` [PATCH-tip 15/22] locking/rwsem: Merge owner into count on x86-64 Waiman Long
2019-02-07 19:45   ` Peter Zijlstra
2019-02-07 19:55     ` Waiman Long
2019-02-07 20:08   ` Peter Zijlstra
2019-02-07 20:54     ` Waiman Long
2019-02-08 14:19       ` Waiman Long
2019-02-07 19:07 ` [PATCH-tip 16/22] locking/rwsem: Remove redundant computation of writer lock word Waiman Long
2019-02-07 19:07 ` [PATCH-tip 17/22] locking/rwsem: Recheck owner if it is not on cpu Waiman Long
2019-02-07 19:07 ` [PATCH-tip 18/22] locking/rwsem: Make rwsem_spin_on_owner() return a tri-state value Waiman Long
2019-02-07 19:07 ` [PATCH-tip 19/22] locking/rwsem: Enable readers spinning on writer Waiman Long
2019-02-07 19:07 ` [PATCH-tip 20/22] locking/rwsem: Enable count-based spinning on reader Waiman Long
2019-02-07 19:07 ` [PATCH-tip 21/22] locking/rwsem: Wake up all readers in wait queue Waiman Long
2019-02-07 19:07 ` [PATCH-tip 22/22] locking/rwsem: Ensure an RT task will not spin on reader Waiman Long
2019-02-07 19:51 ` [PATCH-tip 00/22] locking/rwsem: Rework rwsem-xadd & enable new rwsem features Davidlohr Bueso
2019-02-07 20:00   ` Waiman Long
2019-02-11  7:38     ` Ingo Molnar
2019-02-08 19:50 ` Linus Torvalds [this message]
2019-02-08 20:31   ` Waiman Long
2019-02-09  0:03     ` Linus Torvalds
2019-02-14 13:23     ` Davidlohr Bueso
2019-02-14 15:22       ` Waiman Long
2019-02-13  9:19 ` Chen Rong
2019-02-13 19:56   ` Linus Torvalds
2019-04-10  8:15     ` huang ying
2019-04-10 16:08       ` Waiman Long
2019-04-12  0:49         ` huang ying

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAHk-=wjfyrFBjifzmgMVrkrvEePEPaBTDq7D=f2i5kD2E=SqRQ@mail.gmail.com' \
    --to=torvalds@linux-foundation.org \
    --cc=akpm@linux-foundation.org \
    --cc=arnd@arndb.de \
    --cc=bp@alien8.de \
    --cc=dave@stgolabs.net \
    --cc=hpa@zytor.com \
    --cc=linux-alpha@vger.kernel.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-hexagon@vger.kernel.org \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-sh@vger.kernel.org \
    --cc=linux-xtensa@linux-xtensa.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=longman@redhat.com \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=sparclinux@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=tim.c.chen@linux.intel.com \
    --cc=will.deacon@arm.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linuxppc-dev/0 linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ https://lore.kernel.org/linuxppc-dev \
		linuxppc-dev@lists.ozlabs.org linuxppc-dev@ozlabs.org
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.ozlabs.lists.linuxppc-dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git