Decrease the kHashbits to 12 effectively restoring the pre-r89459 size

Decrease the kHashbits to 12 effectively restoring the pre-r89459 size
of the page heap.

TBR=antonm
TEST=VM usage drops on the perf bots
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=89670

[Alexander Potapenko, 2011-06-20 15:08:11]

TBR

[antonm, 2011-06-20 15:19:04]

Thanks!

On Mon, Jun 20, 2011 at 7:08 PM,  <glider@chromium.org> wrote:
> Reviewers: antonm,
>
> Message:
> TBR
>
> Description:
> Decrease the kHashbits to 12 effectively restoring the pre-r89459 size
> of the page heap.
>
> Please review this at http://codereview.chromium.org/7200028/
>
> SVN Base: svn://svn.chromium.org/chrome/trunk/src/
>
> Affected files:
>  M     third_party/tcmalloc/chromium/src/packed-cache-inl.h
>
>
> Index: third_party/tcmalloc/chromium/src/packed-cache-inl.h
> ===================================================================
> --- third_party/tcmalloc/chromium/src/packed-cache-inl.h        (revision
> 89657)
> +++ third_party/tcmalloc/chromium/src/packed-cache-inl.h        (working
> copy)
> @@ -139,7 +139,9 @@
>   // Decrease the size map cache if running in the small memory mode.
>   static const int kHashbits = 12;
>  #else
> -  static const int kHashbits = 16;
> +  // We don't want the hash map to occupy 512K memory at Chromium, so
> +  // kHashbits is decreased from 16 to 12.
> +  static const int kHashbits = 12;
>  #endif
>   static const int kValuebits = 7;
>   static const bool kUseWholeKeys = kKeybits + kValuebits <= 8 * sizeof(T);
>
>
>

[jar (doing other things), 2011-06-20 16:45:01]

http://codereview.chromium.org/7200028/diff/5001/third_party/tcmalloc/chromiu...
File third_party/tcmalloc/chromium/src/packed-cache-inl.h (right):

http://codereview.chromium.org/7200028/diff/5001/third_party/tcmalloc/chromiu...
third_party/tcmalloc/chromium/src/packed-cache-inl.h:143: // kHashbits is
decreased from 16 to 12.
Question: Rather than forking this file, why don't we just work to set the
TCMALLOC_SMALL_SLOW flag (in Chromium), and get this without a file change?