From: David Laight <David.Laight@ACULAB.COM>
To: 'James Simmons' <jsimmons@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
Andreas Dilger <andreas.dilger@intel.com>,
"Oleg Drokin" <oleg.drokin@intel.com>,
Lai Siyao <lai.siyao@intel.com>,
"Jinshan Xiong" <jinshan.xiong@intel.com>,
NeilBrown <neilb@suse.com>
Cc: Gu Zheng <gzheng@ddn.com>, Li Xi <lixi@ddn.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lustre Development List <lustre-devel@lists.lustre.org>
Subject: RE: [PATCH 1/4] staging: lustre: obdclass: change spinlock of key to rwlock
Date: Thu, 3 May 2018 13:50:07 +0000 [thread overview]
Message-ID: <a3594bd7c393418c8fda5150a075ff1a@AcuMS.aculab.com> (raw)
In-Reply-To: <1525285308-15347-2-git-send-email-jsimmons@infradead.org>
From: James Simmons
> Sent: 02 May 2018 19:22
> From: Li Xi <lixi@ddn.com>
>
> Most of the time, keys are never changed. So rwlock might be
> better for the concurrency of key read.
OTOH unless there is contention on the spin lock during reads the
additional cost of a rwlock (probably double that of a spinlock)
will hurt performance.
...
> - spin_lock(&lu_keys_guard);
> + read_lock(&lu_keys_guard);
> atomic_inc(&lu_key_initing_cnt);
> - spin_unlock(&lu_keys_guard);
> + read_unlock(&lu_keys_guard);
WTF, seems unlikely that you need to hold any kind of lock
over an atomic_inc().
If this is just ensuring that no code holds the lock then
it would need to request the write_lock().
(and would need a comment)
David
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next prev parent reply other threads:[~2018-05-03 13:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-02 18:21 [PATCH 0/4] staging: lustre: obdclass: missing lu_object fixes James Simmons
2018-05-02 18:21 ` [PATCH 1/4] staging: lustre: obdclass: change spinlock of key to rwlock James Simmons
2018-05-03 13:50 ` David Laight [this message]
2018-05-03 23:26 ` NeilBrown
2018-05-04 0:11 ` Dilger, Andreas
2018-05-04 0:53 ` NeilBrown
2018-05-02 18:21 ` [PATCH 2/4] staging: lustre: obdclass: hoist locking in lu_context_exit() James Simmons
2018-05-02 18:21 ` [PATCH 3/4] staging: lustre: obdclass: guarantee all keys filled James Simmons
2018-05-02 18:21 ` [PATCH 4/4] staging: lustre: obdclass: change object lookup to no wait mode James Simmons
2018-05-04 1:15 ` NeilBrown
2018-05-15 0:37 ` James Simmons
2018-05-15 1:37 ` NeilBrown
2018-05-15 2:11 ` James Simmons
2018-05-07 1:47 ` Greg Kroah-Hartman
2018-05-08 11:45 ` Dan Carpenter
2018-05-15 15:02 ` James Simmons
2018-05-16 8:00 ` Dan Carpenter
2018-05-16 9:12 ` Dilger, Andreas
2018-05-16 15:44 ` Joe Perches
2018-05-16 16:57 ` Greg Kroah-Hartman
2018-05-17 5:07 ` James Simmons
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