From: Andrew Lunn <andrew@lunn.ch>
To: Umang Jain <umang.jain@ideasonboard.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com>,
Ray Jui <rjui@broadcom.com>, Dan Carpenter <error27@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org,
kieran.bingham@ideasonboard.com
Subject: Re: [PATCH 2/3] vc04_services: mmal-vchiq: Use bool for vchiq_mmal_component.in_use
Date: Fri, 18 Nov 2022 01:23:36 +0100 [thread overview]
Message-ID: <Y3bQiDw11t4pRokP@lunn.ch> (raw)
In-Reply-To: <20221117160015.344528-3-umang.jain@ideasonboard.com>
> struct vchiq_mmal_component {
> - u32 in_use:1;
> + bool in_use:1;
> bool enabled:1;
The patch you referenced says:
+If a structure has many true/false values, consider consolidating them into a
+bitfield with 1 bit members, or using an appropriate fixed width type, such as
+u8.
The code did exactly this, using two bits fields, in one u32. A bool
probably takes up 4 bytes, maybe 8 bytes, so this change probably
doubles the storage size for these two fields. Are these fields on the
hot path, where an extra AND instruction would make a difference?
Andrew
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Lunn <andrew@lunn.ch>
To: Umang Jain <umang.jain@ideasonboard.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
Broadcom internal kernel review list
<bcm-kernel-feedback-list@broadcom.com>,
Ray Jui <rjui@broadcom.com>, Dan Carpenter <error27@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Dave Stevenson <dave.stevenson@raspberrypi.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org,
kieran.bingham@ideasonboard.com
Subject: Re: [PATCH 2/3] vc04_services: mmal-vchiq: Use bool for vchiq_mmal_component.in_use
Date: Fri, 18 Nov 2022 01:23:36 +0100 [thread overview]
Message-ID: <Y3bQiDw11t4pRokP@lunn.ch> (raw)
In-Reply-To: <20221117160015.344528-3-umang.jain@ideasonboard.com>
> struct vchiq_mmal_component {
> - u32 in_use:1;
> + bool in_use:1;
> bool enabled:1;
The patch you referenced says:
+If a structure has many true/false values, consider consolidating them into a
+bitfield with 1 bit members, or using an appropriate fixed width type, such as
+u8.
The code did exactly this, using two bits fields, in one u32. A bool
probably takes up 4 bytes, maybe 8 bytes, so this change probably
doubles the storage size for these two fields. Are these fields on the
hot path, where an extra AND instruction would make a difference?
Andrew
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-11-18 0:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-17 16:00 [PATCH 0/3] vc04_services: Promote bool usage Umang Jain
2022-11-17 16:00 ` Umang Jain
2022-11-17 16:00 ` [PATCH 1/3] Revert "staging: mmal-vchiq: Avoid use of bool in structures" Umang Jain
2022-11-17 16:00 ` Umang Jain
2022-11-17 16:09 ` Kieran Bingham
2022-11-17 16:09 ` Kieran Bingham
2022-11-17 17:55 ` Umang Jain
2022-11-17 17:55 ` Umang Jain
2022-11-17 18:02 ` Greg Kroah-Hartman
2022-11-17 18:02 ` Greg Kroah-Hartman
2022-11-17 18:22 ` Umang Jain
2022-11-17 18:22 ` Umang Jain
2022-11-18 0:12 ` Andrew Lunn
2022-11-18 0:12 ` Andrew Lunn
2022-11-18 3:58 ` Umang Jain
2022-11-18 3:58 ` Umang Jain
2022-11-18 8:35 ` Dan Carpenter
2022-11-18 8:35 ` Dan Carpenter
2022-11-17 16:00 ` [PATCH 2/3] vc04_services: mmal-vchiq: Use bool for vchiq_mmal_component.in_use Umang Jain
2022-11-17 16:00 ` Umang Jain
2022-11-18 0:23 ` Andrew Lunn [this message]
2022-11-18 0:23 ` Andrew Lunn
2022-11-18 9:01 ` Dan Carpenter
2022-11-18 9:01 ` Dan Carpenter
2022-11-17 16:00 ` [PATCH 3/3] vc04_services: bcm2835-camera: Use bool values for mmal_fmt.remove_padding Umang Jain
2022-11-17 16:00 ` Umang Jain
2022-11-17 18:11 ` [PATCH 0/3] vc04_services: Promote bool usage Stefan Wahren
2022-11-17 18:11 ` Stefan Wahren
2022-11-18 8:47 ` Dan Carpenter
2022-11-18 8:47 ` Dan Carpenter
2022-11-18 17:25 ` Dave Stevenson
2022-11-18 17:25 ` Dave Stevenson
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