RFR (S): Pre-touch bitmaps

[Roman Kennke]

Yes in general.

But is it worth dividing pretouching the bitmaps between the workers?
Maybe one worker should pretouch one bitmap, another the other bitmap,
and the rest start pretouching the heap? Not sure, and probably not
very important...

Roman

Am Mittwoch, den 01.02.2017, 21:57 +0100 schrieb Aleksey Shipilev:
> Hi,
> 
> Turns out, pre-touching bitmaps helps for the same reason pre-
> touching regions
> helps. So, we can touch the bitmaps when touching the regions too:
>   http://cr.openjdk.java.net/~shade/shenandoah/bitmaps-pretouch/webre
> v.01/
> 
> Previous incarnation of the patch improved reset times:
> 
>   baseline: Reset Bitmaps = 5.52 s (a =   204332 us) (n =    27)
>              (lvls, us
> =     7402,   197266,   214844,   232422,   258593)
> 
> pretouched: Reset Bitmaps = 2.34 s (a =    86509 us) (n =    27)
>              (lvls, us
> =     1113,    81641,    88086,   101562,   117187)
> 
> I will retest this on the same machine once it is free.
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
>