Re: [PATCH V6 01/17] perf, x86: Reduce lbr_sel_map size

From: Peter Zijlstra
Date: Fri Oct 24 2014 - 05:39:42 EST


On Sun, Oct 19, 2014 at 05:54:56PM -0400, Kan Liang wrote:

This should still very much have:

From: Yan, Zheng <zheng.z.yan@xxxxxxxxx>

Seeing how you did not write this patch, probably true for all the
others too, although I've not checked yet.

> The index of lbr_sel_map is bit value of perf branch_sample_type.
> PERF_SAMPLE_BRANCH_MAX is 1024 at present, so each lbr_sel_map uses
> 4096 bytes. By using bit shift as index, we can reduce lbr_sel_map
> size to 40 bytes. This patch defines 'bit shift' for branch types,
> and use 'bit shift' to define lbr_sel_maps.
>
> Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
> Reviewed-by: Stephane Eranian <eranian@xxxxxxxxxx>
> ---

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