> Greetings,
> I've dedusted the guest page hinting patches and ported them to todays
> upstream git tree. There is one reject if applied to 2.6.24-rc5-mm1 but
> that is easy to fix. The code stills works as expected on my test system.
>
> Our z/VM performance team recently published a report on guest page
> hinting vs. the ballooner approach on SLES10 for a farm of web servers.
> The code on SLES10 differs a bit from the upstream variant but the
> performance results should be still valid. You will find the report
> here:
>
>
http://www.vm.ibm.com/perf/reports/zvm/html/530cmm.html
>
> (the VMRM-CMM the web page speaks about is the balloon approach,
> CMMA is the guest page hinting).
>
> Both approaches to the memory overcommit problem show comparable benefits
> for this workload, with an advantage for guest page hinting for large
> number of guests. For other workloads your mileage may vary.
>
> The main benefit for guest page hinting vs. the ballooner is that there
> is no need for a monitor that keeps track of the memory usage of all the
> guests, a complex algorithm that calculates the working set sizes and for
> the calls into the guest kernel to control the size of the balloons.
> The host just does normal LRU based paging. If the host picks one of the
> pages the guest can recreate, the host can throw it away instead of writing
> it to the paging device. Simple and elegant.
> The main disadvantage is the added complexity that is introduced to the
> guests memory management code to do the page state changes and to deal
> with discard faults.
>
> The last versions of the patches do not differ much, I consider the code
> to be stable. My question now is how to proceed with the code. I sure
> would love to see the code going upstream some day but that depends on
> the mm developers as the code adds complexity that needs to be supported.
> If the general feeling is that the advantages of this approach do not
> warrent for the added complexity this will likely be the last time you
> will hear about guest page hinting.
