From: Bart Van Assche <bvanassche@acm.org>
To: Sagi Grimberg <sagi@grimberg.me>,
Johannes Thumshirn <jthumshirn@suse.de>,
Jens Axboe <axboe@fb.com>
Cc: Linux Block Layer Mailinglist <linux-block@vger.kernel.org>,
Hannes Reinecke <hare@suse.de>,
Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>,
Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] block: respect virtual boundary mask in bvecs
Date: Wed, 07 Nov 2018 08:10:19 -0800 [thread overview]
Message-ID: <1541607019.196084.210.camel@acm.org> (raw)
In-Reply-To: <950a7996-e0f7-ff34-04da-47581a9496f0@grimberg.me>
On Tue, 2018-11-06 at 19:30 -0800, Sagi Grimberg wrote:
> > > How about changing that expression into the following to make it easier
> > > for the compiler to optimize this code?
> > >
> > > (offset | (bprv->bv_offset + bprv->bv_len)) & queue_virt_boundary(q)
> >
> > Uhm I have to admit I'm not really able to parse the above expression.
> > Sure GCC will do it but I think it's less readable (at least for me).
> > Let's see what other's think.
>
> I personally not a huge fan of decoding complicated expressions. But if
> others are fine with it then I am too...
What I proposed is not a new pattern. It is a pattern that is already used
elsewhere in the Linux kernel. A few examples:
>From dmabounce.c:
/* Figure out if we need to bounce from the DMA mask. */
if ((dma_addr | (dma_addr + size - 1)) & ~mask)
return 1;
>From dma-direct.h:
if ((addr | (addr + size - 1)) & ~mask)
return 0;
Bart.
WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <bvanassche@acm.org>
To: Sagi Grimberg <sagi@grimberg.me>,
Johannes Thumshirn <jthumshirn@suse.de>,
Jens Axboe <axboe@fb.com>
Cc: Linux Block Layer Mailinglist <linux-block@vger.kernel.org>,
Hannes Reinecke <hare@suse.de>,
Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>,
Jan Kara <jack@suse.cz>
Subject: Re: [PATCH] block: respect virtual boundary mask in bvecs
Date: Wed, 07 Nov 2018 08:10:19 -0800 [thread overview]
Message-ID: <1541607019.196084.210.camel@acm.org> (raw)
In-Reply-To: <950a7996-e0f7-ff34-04da-47581a9496f0@grimberg.me>
On Tue, 2018-11-06 at 19:30 -0800, Sagi Grimberg wrote:
> > > How about changing that expression into the following to make it easier
> > > for the compiler to optimize this code?
> > >
> > > (offset | (bprv->bv_offset + bprv->bv_len)) & queue_virt_boundary(q)
> >
> > Uhm I have to admit I'm not really able to parse the above expression.
> > Sure GCC will do it but I think it's less readable (at least for me).
> > Let's see what other's think.
>
> I personally not a huge fan of decoding complicated expressions. But if
> others are fine with it then I am too...
What I proposed is not a new pattern. It is a pattern that is already used
elsewhere in the Linux kernel. A few examples:
From dmabounce.c:
/* Figure out if we need to bounce from the DMA mask. */
if ((dma_addr | (dma_addr + size - 1)) & ~mask)
return 1;
From dma-direct.h:
if ((addr | (addr + size - 1)) & ~mask)
return 0;
Bart.
next prev parent reply other threads:[~2018-11-08 1:41 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 10:23 [PATCH] block: respect virtual boundary mask in bvecs Johannes Thumshirn
2018-11-05 10:55 ` Ming Lei
2018-11-05 11:50 ` Johannes Thumshirn
2018-11-05 12:01 ` Ming Lei
2018-11-06 12:34 ` Johannes Thumshirn
2018-11-06 14:56 ` Ming Lei
2018-11-06 15:14 ` Keith Busch
2018-11-07 3:14 ` Sagi Grimberg
2018-11-07 3:11 ` Sagi Grimberg
2018-11-06 14:31 ` Keith Busch
2018-11-06 14:53 ` Bart Van Assche
2018-11-06 14:56 ` Johannes Thumshirn
2018-11-07 3:30 ` Sagi Grimberg
2018-11-07 16:10 ` Bart Van Assche [this message]
2018-11-07 16:10 ` Bart Van Assche
2018-11-08 15:04 ` Christoph Hellwig
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