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SubjectRe: [PATCH 2/2] staging: zcache: optional support for zsmalloc as alternate allocator
On Wed, Jan 23, 2013 at 01:46:31PM -0800, Dan Magenheimer wrote:
> "New" zcache uses zbud for all sub-page allocation which is more flexible but
> results in lower density. "Old" zcache supported zsmalloc for frontswap
> pages. Add zsmalloc to "new" zcache as a compile-time and run-time option
> for backwards compatibility in case any users wants to use zcache with
> highest possible density.
>
> Note that most of the zsmalloc stats in old zcache are not included here
> because old zcache used sysfs and new zcache has converted to debugfs.
> These stats may be added later.
>
> Note also that ramster is incompatible with zsmalloc as the two use
> the least significant bits in a pampd differently.
>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
> ---
> drivers/staging/zcache/Kconfig | 11 ++
> drivers/staging/zcache/zcache-main.c | 210 ++++++++++++++++++++++++++++++++--
> drivers/staging/zcache/zcache.h | 3 +
> 3 files changed, 215 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/staging/zcache/Kconfig b/drivers/staging/zcache/Kconfig
> index c1dbd04..116f8d5 100644
> --- a/drivers/staging/zcache/Kconfig
> +++ b/drivers/staging/zcache/Kconfig
> @@ -10,6 +10,17 @@ config ZCACHE
> memory to store clean page cache pages and swap in RAM,
> providing a noticeable reduction in disk I/O.
>
> +config ZCACHE_ZSMALLOC
> + bool "Allow use of zsmalloc allocator for compression of swap pages"
> + depends on ZSMALLOC=y && !RAMSTER
> + default n
> + help
> + Zsmalloc is a much more efficient allocator for compresssed
> + pages but currently has some design deficiencies in that it
> + does not support reclaim nor compaction. Select this if
> + you are certain your workload will fit or has mostly short
> + running processes. Zsmalloc is incompatible with RAMster.

How can anyone be "certain"?


> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -26,6 +26,12 @@
> #include <linux/cleancache.h>
> #include <linux/frontswap.h>
> #include "tmem.h"
> +#ifdef CONFIG_ZCACHE_ZSMALLOC
> +#include "../zsmalloc/zsmalloc.h"

Don't #ifdef .h files in .c files.

> +static int zsmalloc_enabled;
> +#else
> +#define zsmalloc_enabled 0
> +#endif

That should have been your only ifdef in this .c file, all of the ones
you have after this should not be needed, so I can't take this patch,
sorry.

thanks,

greg k-h


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