Re: Re: Performance degradation seen after using one list for hot/cold pages.

Re: Re: Performance degradation seen after using one list for hot/cold pages.

[NARAYANAN GOPALAKRISHNAN]

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> I'll add the rather important text:
> 
> Fix a post-2.6.24 performance regression caused by
> 3dfa5721f12c3d5a441448086bee156887daa961 ("page-allocator: preserve PFN
> ordering when __GFP_COLD is set").
>
> This was a pretty major screwup.
>
> This is why changing core MM is so worrisome - there's so much secret and
> subtle history to it, and performance dependencies are unobvious and quite
> indirect and the lag time to discover regressions is long.
> 
> Narayanan, are you able to quantify the regression more clearly?  All I
> have is "2 MBps lower" which isn't very useful.  What is this as a
> percentage, and with what sort of disk controller?  Thanks.

It is around 15%. There is no disk controller as our setup is based on Samsung OneNAND
used as a memory mapped device on a OMAP2430 based board.

Narayanan
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