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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH QEMU] Transparent Hugepage Support #2
Date: Tue, 16 Mar 2010 23:48:39 +0000
References: <20100316164641.GB5717@random.random>
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To: qemu-devel@nongnu.org
Cc: Andrea Arcangeli <aarcange@redhat.com>, Avi Kivity <avi@redhat.com>

> +#if defined(__linux__) && defined(__x86_64__)
> +#define MAX_TRANSPARENT_HUGEPAGE_SIZE (2*1024*1024)
> +       if (size >= MAX_TRANSPARENT_HUGEPAGE_SIZE)

I'd prefer something like:

#if defined(__linux__) && defined(__x86_64__)
/* [...Allow the host to use huge pages easily...].  */
#define PREFERRED_RAM_ALIGN (2*1024*1024)
#endif

qemu_ram_alloc(...)
{...
#ifdef PREFERRED_RAM_ALIGN
  if ((size & (PREFERRED_RAM_ALIGN - 1)) == 0) {
    new_block->host = qemu_memalign(...)
  }
#endif


i.e. separate the architecture specific knowledge from the generic alignment 
code.

Paul