lkml.org 
[lkml]   [2018]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] block: respect virtual boundary mask in bvecs
From
Date
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.

\
 
 \ /
  Last update: 2018-11-07 17:10    [W:0.096 / U:3.628 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site