linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Waiman Long <Waiman.Long@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-s390@vger.kernel.org, linux-arch@vger.kernel.org,
	xfs@oss.sgi.com, Davidlohr Bueso <dave@stgolabs.net>,
	Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
	Scott J Norton <scott.norton@hpe.com>,
	Douglas Hatch <doug.hatch@hpe.com>,
	Waiman Long <Waiman.Long@hpe.com>
Subject: [RFC PATCH-tip 0/6] locking/rwsem: Enable reader optimistic spinning
Date: Tue, 14 Jun 2016 14:12:33 -0400	[thread overview]
Message-ID: <1465927959-39719-1-git-send-email-Waiman.Long@hpe.com> (raw)

This patchset adds an option to enable more aggressive optimistic
spinning on both readers and writers waiting on a writer or reader
owned lock. Spinning on writer is done by looking at the on_cpu
flag of the lock owner. Spinning on readers, on the other hand, is
count-based as there is no easy way to figure out if all the readers
are running. The spinner will stop spinning once the count goes to
0. Because of that, spinning on readers may hurt performance in some
cases. So this feature is optional and has to explicitly enabled for
those rwsems where the readers are unlikely to go to sleep.

Patch 1 reduces the length of the blocking window after a read locking
attempt where writer lock stealing is disabled because of the active
read lock. It can improve rwsem performance for contended lock. It is
independent of the rest of the patchset.

Patches 2-5 lays the groundwork for enabling reader optimistic spinning.

Patch 6 enables reader optimistic spinning in XFS for inodes that
comes from a DAX-enabled mount point on top of persistent memory as
the CPUs can do I/O directly without waiting or sleeping.

Waiman Long (6):
  locking/rwsem: Stop active read lock ASAP
  locking/rwsem: Enable optional count-based spinning on reader
  locking/rwsem: move down rwsem_down_read_failed function
  locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation
  locking/rwsem: Enable spinning readers
  xfs: Enable reader optimistic spinning for DAX inodes

 arch/alpha/include/asm/rwsem.h |    7 +-
 arch/ia64/include/asm/rwsem.h  |    6 +-
 arch/s390/include/asm/rwsem.h  |    6 +-
 arch/x86/include/asm/rwsem.h   |   13 ++-
 fs/xfs/xfs_icache.c            |    9 ++
 include/asm-generic/rwsem.h    |    9 +-
 include/linux/rwsem.h          |   21 ++++-
 kernel/locking/rwsem-xadd.c    |  212 ++++++++++++++++++++++++++--------------
 8 files changed, 192 insertions(+), 91 deletions(-)

             reply	other threads:[~2016-06-14 18:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-14 18:12 Waiman Long [this message]
2016-06-14 18:12 ` [RFC PATCH-tip 1/6] locking/rwsem: Stop active read lock ASAP Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 2/6] locking/rwsem: Enable optional count-based spinning on reader Waiman Long
2016-06-14 18:27   ` Davidlohr Bueso
2016-06-14 19:11     ` Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 3/6] locking/rwsem: move down rwsem_down_read_failed function Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 4/6] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 5/6] locking/rwsem: Enable spinning readers Waiman Long
2016-06-14 18:12 ` [RFC PATCH-tip 6/6] xfs: Enable reader optimistic spinning for DAX inodes Waiman Long
2016-06-14 18:24   ` Christoph Hellwig
2016-06-14 19:08     ` Waiman Long
2016-06-14 23:06   ` Dave Chinner
2016-06-15 18:55     ` Waiman Long

Reply instructions:

You may reply publicly 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=1465927959-39719-1-git-send-email-Waiman.Long@hpe.com \
    --to=waiman.long@hpe.com \
    --cc=dave@stgolabs.net \
    --cc=david@fromorbit.com \
    --cc=doug.hatch@hpe.com \
    --cc=jason.low2@hp.com \
    --cc=linux-alpha@vger.kernel.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=scott.norton@hpe.com \
    --cc=x86@kernel.org \
    --cc=xfs@oss.sgi.com \
    --subject='Re: [RFC PATCH-tip 0/6] locking/rwsem: Enable reader optimistic spinning' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).