From: Waiman Long <waiman.long@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Scott J Norton <scott.norton@hp.com>,
Douglas Hatch <doug.hatch@hp.com>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v6 5/6] locking/pvqspinlock: Allow 1 lock stealing attempt
Date: Mon, 14 Sep 2015 15:02:52 -0400 [thread overview]
Message-ID: <55F719DC.5040607@hpe.com> (raw)
In-Reply-To: <20150914135749.GS18489@twins.programming.kicks-ass.net>
On 09/14/2015 09:57 AM, Peter Zijlstra wrote:
> On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:
>> +#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l)
>> +static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock)
>> +{
>> + struct __qspinlock *l = (void *)lock;
>> +
>> + if (READ_ONCE(l->locked))
>> + return 0;
>> + /*
>> + * Wait a bit here to ensure that an actively spinning vCPU has a fair
>> + * chance of getting the lock.
>> + */
>> + cpu_relax();
>> +
>> + return cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0;
>> +}
>> +static inline int pvstat_trylock_unfair(struct qspinlock *lock)
>> +{
>> + int ret = pv_queued_spin_trylock_unfair(lock);
>> +
>> + if (ret)
>> + pvstat_inc(pvstat_utrylock);
>> + return ret;
>> +}
>> +#undef queued_spin_trylock
>> +#define queued_spin_trylock(l) pvstat_trylock_unfair(l)
> These aren't actually ever used...
The pvstat_trylock_unfair() is within the CONFIG_QUEUED_LOCK_STAT block.
It will only be activated when the config parameter is set. Otherwise,
pv_queued_spin_trylock_unfair() will be used without any counting.
It is used provide count of how many unfair trylock has successfully got
the lock.
Cheers,
Longman
next prev parent reply other threads:[~2015-09-14 19:02 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-11 18:37 [PATCH v6 0/6] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-09-11 18:37 ` [PATCH v6 1/6] locking/qspinlock: relaxes cmpxchg & xchg ops in native code Waiman Long
2015-09-11 22:27 ` Davidlohr Bueso
2015-09-14 12:06 ` Peter Zijlstra
2015-09-14 18:40 ` Waiman Long
2015-09-14 15:16 ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 2/6] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long
2015-09-18 8:50 ` [tip:locking/core] locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL tip-bot for Waiman Long
2015-09-11 18:37 ` [PATCH v6 3/6] locking/pvqspinlock, x86: Optimize PV unlock code path Waiman Long
2015-09-11 18:37 ` [PATCH v6 4/6] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-09-11 23:13 ` Davidlohr Bueso
2015-09-14 15:25 ` Waiman Long
2015-09-14 21:41 ` Davidlohr Bueso
2015-09-15 3:47 ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 5/6] locking/pvqspinlock: Allow 1 lock stealing attempt Waiman Long
2015-09-14 13:57 ` Peter Zijlstra
2015-09-14 19:02 ` Waiman Long [this message]
2015-09-14 14:00 ` Peter Zijlstra
2015-09-14 19:15 ` Waiman Long
2015-09-14 19:38 ` Waiman Long
2015-09-15 8:24 ` Peter Zijlstra
2015-09-15 15:29 ` Waiman Long
2015-09-16 15:01 ` Peter Zijlstra
2015-09-17 15:08 ` Waiman Long
2015-09-14 14:04 ` Peter Zijlstra
2015-09-14 19:19 ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 6/6] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
2015-09-14 14:10 ` Peter Zijlstra
2015-09-14 19:37 ` Waiman Long
2015-09-15 8:38 ` Peter Zijlstra
2015-09-15 15:32 ` Waiman Long
2015-09-16 15:03 ` Peter Zijlstra
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=55F719DC.5040607@hpe.com \
--to=waiman.long@hpe.com \
--cc=dave@stgolabs.net \
--cc=doug.hatch@hp.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=scott.norton@hp.com \
--cc=tglx@linutronix.de \
--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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.