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SubjectRe: [PATCH 3/3] seq_file: convert seq buffer to vmalloc
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On Thu, 2011-09-22 at 14:07 -0700, Joe Perches wrote:
> On Thu, 2011-09-22 at 13:57 -0700, Colin Cross wrote:
> > seq_files are often used for debugging. When things are going wrong
> > due to failed physically contiguous allocations, the exponentially
> > growing physically contiguous allocations in seq_read can make things
> > worse. There is no need for physically contiguous memory, so switch
> > to virtually contiguous memory instead.
>
> vmalloc's are relatively expensive.

And very limited on certain archs..

> Perhaps use kmalloc when appropriate instead?
>
> []
> > - /* don't ask for more than the kmalloc() max size */
> > - if (size > KMALLOC_MAX_SIZE)
> > - size = KMALLOC_MAX_SIZE;
> > -
> > - buf = kmalloc(size, GFP_KERNEL);
> > + buf = vmalloc(size);
> > if (!buf)
> > return -ENOMEM;
>
> if (size > KMALLOC_MAX_SIZE)
> buf = vmalloc(size, GFP_KERNEL)
> else
> buf = kmalloc(size, GFP_KERNEL)

There's wrappers for this stuff IIRC, that said all this is a horrible
idea. Just avoid the situation instead of coping with it.


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