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Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux

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On Monday 14 September 2015 13:04:59 Roger Pau Monné wrote:
> > TBH, I'm expecting a small impact to the performance. It would be hard
> > to get the exactly the same performance as today if we keep the helpers
> > to avoid the backend dealing himself with the splitting and page
> > granularity.
> > 
> > Although, if the performance impact is not acceptable, it may be
> > possible to optimize gnttab_foreach_grant_in_range by moving the
> > function inline. The current way to the loop is the fastest I've found
> > (I've wrote a small program to test different way) and we will need it
> > when different of size will be supported.
> 
> I don't expect the performance to drop massively with this patches
> applied, but it would be good to al least have an idea of the impact.

Note that using 64kb pages in Linux tends to destroy performance
in Linux in any case, as the memory consumption for most workloads
explodes. In a virtualized environment you already tend to be
memory constrained, so any measurement should take that into account
and put the extra overhead into perspective to the massive overhead
of running 64kb pages when RAM is tight.

	Arnd
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[PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:40 +0200
  [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:40 +0200
    Re: [PATCH v4 12/20] xen/balloon: Don't rely on the page granularity  is the same for Xen and Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-07 18:50 +0200
  [PATCH v4 15/20] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
  [PATCH v4 20/20] arm/xen: Add support for 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
  [PATCH v4 17/20] net/xen-netfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
  [PATCH v4 10/20] xen/xenbus: Use Xen page definition Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
  [PATCH v4 16/20] block/xen-blkback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
  [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-07 17:50 +0200
    Re: [PATCH v4 18/20] net/xen-netback: Make it running on 64KB page  granularity Wei Liu <wei.liu2@citrix.com> - 2015-09-07 19:00 +0200
      Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running on  64KB page granularity Wei Liu <wei.liu2@citrix.com> - 2015-09-08 13:10 +0200
      Re: [Xen-devel] [PATCH v4 18/20] net/xen-netback: Make it running  on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-08 13:10 +0200
  Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB  page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-11 21:50 +0200
  Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 11:00 +0200
    Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 12:50 +0200
      Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 13:10 +0200
        Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 13:30 +0200
          Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 14:10 +0200
            Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 14:50 +0200
              Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 16:40 +0200
                Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-14 16:50 +0200
                Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-09-14 17:00 +0200
                Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Roger Pau Monné <roger.pau@citrix.com> - 2015-09-14 17:30 +0200
            Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Julien Grall <julien.grall@citrix.com> - 2015-09-18 16:20 +0200
        Re: [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Arnd Bergmann <arnd@arndb.de> - 2015-09-14 13:40 +0200
          Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB  page in Linux David Vrabel <david.vrabel@citrix.com> - 2015-09-15 15:20 +0200
            Re: [Xen-devel] [PATCH v4 00/20] xen/arm64: Add support for 64KB page in Linux Arnd Bergmann <arnd@arndb.de> - 2015-09-15 15:30 +0200

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