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SubjectRe: [PATCH] zsmalloc: Add Kconfig for enabling PTE method
On Tue, Feb 05, 2013 at 09:08:54AM +0900, Minchan Kim wrote:
> Hi Greg,
>
> On Mon, Feb 04, 2013 at 10:51:46AM -0800, Greg Kroah-Hartman wrote:
> > On Mon, Feb 04, 2013 at 09:23:41AM +0900, Minchan Kim wrote:
> > > Zsmalloc has two methods 1) copy-based and 2) pte based to access
> > > allocations that span two pages.
> > > You can see history why we supported two approach from [1].
> > >
> > > But it was bad choice that adding hard coding to select architecture
> > > which want to use pte based method. This patch removed it and adds
> > > new Kconfig to select the approach.
> > >
> > > This patch is based on next-20130202.
> > >
> > > [1] https://lkml.org/lkml/2012/7/11/58
> > >
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
> > > Cc: Nitin Gupta <ngupta@vflare.org>
> > > Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
> > > Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>
> > > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > > ---
> > > drivers/staging/zsmalloc/Kconfig | 12 ++++++++++++
> > > drivers/staging/zsmalloc/zsmalloc-main.c | 11 -----------
> > > 2 files changed, 12 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
> > > index 9084565..2359123 100644
> > > --- a/drivers/staging/zsmalloc/Kconfig
> > > +++ b/drivers/staging/zsmalloc/Kconfig
> > > @@ -8,3 +8,15 @@ config ZSMALLOC
> > > non-standard allocator interface where a handle, not a pointer, is
> > > returned by an alloc(). This handle must be mapped in order to
> > > access the allocated space.
> > > +
> > > +config ZSMALLOC_PGTABLE_MAPPING
> > > + bool "Use page table mapping to access allocations that span two pages"
> > > + depends on ZSMALLOC
> > > + default n
> > > + help
> > > + By default, zsmalloc uses a copy-based object mapping method to access
> > > + allocations that span two pages. However, if a particular architecture
> > > + performs VM mapping faster than copying, then you should select this.
> > > + This causes zsmalloc to use page table mapping rather than copying
> > > + for object mapping. You can check speed with zsmalloc benchmark[1].
> > > + [1] https://github.com/spartacus06/zsmalloc
> > > diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> > > index 06f73a9..b161ca1 100644
> > > --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> > > +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> > > @@ -218,17 +218,6 @@ struct zs_pool {
> > > #define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)
> > > #define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)
> > >
> > > -/*
> > > - * By default, zsmalloc uses a copy-based object mapping method to access
> > > - * allocations that span two pages. However, if a particular architecture
> > > - * performs VM mapping faster than copying, then it should be added here
> > > - * so that USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use
> > > - * page table mapping rather than copying for object mapping.
> > > -*/
> > > -#if defined(CONFIG_ARM)
> > > -#define USE_PGTABLE_MAPPING
> > > -#endif
> >
> > Did you test this? I don't see the new config value you added actually
> > do anything in this code. Also, if I select it incorrectly on ARM, or
>
> *slaps self*

Ok, so I'll drop this patch now. As for what to do instead, I have no
idea, sorry, but the others should.

thanks,

greg k-h


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