From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Davidlohr Bueso <dave@stgolabs.net>,
peterz@infradead.org, mingo@kernel.org
Cc: davem@davemloft.net, cw00.choi@samsung.com,
dougthompson@xmission.com, bp@alien8.de, mchehab@osg.samsung.com,
gregkh@linuxfoundation.org, pfg@sgi.com, jikos@kernel.org,
hans.verkuil@cisco.com, awalls@md.metrocast.net,
dledford@redhat.com, sean.hefty@intel.com, kys@microsoft.com,
heiko.carstens@de.ibm.com, sumit.semwal@linaro.org,
schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -tip 00/12] locking/atomics: Add and use inc,dec calls for FETCH-OP flavors
Date: Fri, 24 Jun 2016 09:46:05 -0700 [thread overview]
Message-ID: <1466786765.2343.37.camel@HansenPartnership.com> (raw)
In-Reply-To: <1466453164-13185-1-git-send-email-dave@stgolabs.net>
On Mon, 2016-06-20 at 13:05 -0700, Davidlohr Bueso wrote:
> Hi,
>
> The series is really straightforward and based on Peter's work that
> introduces[1] the atomic_fetch_$op machinery. Only patch 1 implements
> the actual atomic_fetch_{inc,dec} calls based on
> atomic_fetch_{add,sub}.
Could I just ask why? atomic_inc_return(x) - 1 seems a reasonable
thing to do to me. Is it because on architectures where atomics are
implemented in asm, it costs us one more CPU instruction to do the
extra decrement which gcc can't optimise? If that's it, I'm not sure
the added complexity justifies the cycle savings.
James
next prev parent reply other threads:[~2016-06-24 16:46 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-20 20:05 [PATCH -tip 00/12] locking/atomics: Add and use inc,dec calls for FETCH-OP flavors Davidlohr Bueso
2016-06-20 20:05 ` [PATCH 01/12] locking/atomic: Introduce inc/dec " Davidlohr Bueso
2016-06-21 7:28 ` Peter Zijlstra
2016-06-21 13:33 ` [PATCH v2 " Davidlohr Bueso
2016-06-21 16:36 ` Davidlohr Bueso
2016-06-23 9:09 ` Peter Zijlstra
2016-06-24 16:34 ` Davidlohr Bueso
2016-06-24 18:48 ` Peter Zijlstra
2016-06-28 21:56 ` [PATCH -v4 " Davidlohr Bueso
2016-07-07 8:33 ` [tip:locking/core] locking/atomic: Introduce inc/dec variants for the atomic_fetch_$op() API tip-bot for Davidlohr Bueso
2016-06-20 20:05 ` [PATCH 02/12] net/neighbour: Employ atomic_fetch_inc() Davidlohr Bueso
2016-06-20 20:05 ` [PATCH 03/12] PM,devfreq: " Davidlohr Bueso
2016-07-02 5:04 ` Chanwoo Choi
2016-06-20 20:05 ` [PATCH 04/12] EDAC: " Davidlohr Bueso
2016-06-21 13:59 ` Borislav Petkov
2016-06-20 20:05 ` [PATCH 05/12] tty/serial: " Davidlohr Bueso
2016-06-20 20:05 ` [PATCH 06/12] HID,wacom: " Davidlohr Bueso
2016-06-22 8:10 ` Jiri Kosina
2016-06-20 20:05 ` [PATCH 07/12] drivers/media: " Davidlohr Bueso
2016-07-13 16:07 ` Mauro Carvalho Chehab
2016-06-20 20:06 ` [PATCH 08/12] infiniband: " Davidlohr Bueso
2016-06-20 20:06 ` [PATCH 09/12] drivers/hv: " Davidlohr Bueso
2016-06-20 20:06 ` [PATCH 10/12] s390/scm_block: " Davidlohr Bueso
2016-06-20 20:06 ` [PATCH 11/12] scsi: " Davidlohr Bueso
2016-06-20 20:06 ` [PATCH 12/12] dma-buf/fence: Employ atomic_fetch_add Davidlohr Bueso
2016-06-24 16:46 ` James Bottomley [this message]
2016-06-24 17:30 ` [PATCH -tip 00/12] locking/atomics: Add and use inc,dec calls for FETCH-OP flavors Davidlohr Bueso
2016-06-24 17:44 ` James Bottomley
2016-06-24 20:35 ` Davidlohr Bueso
2016-06-24 17:45 ` KY Srinivasan
2016-06-24 19:35 ` Davidlohr Bueso
2016-06-24 19:17 ` Peter Zijlstra
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