Re: [PATCH v2 1/3] zsmalloc: support zsmalloc to ARM, MIPS, SUPERH

[Guan Xuetao <gxt@mprc.pku.edu.cn>]

On Wed, 2012-05-16 at 11:05 +0900, Minchan Kim wrote:
> zsmalloc uses set_pte and __flush_tlb_one for performance but
> many architecture don't support it. so this patch removes
> set_pte and __flush_tlb_one which are x86 dependency.
> Instead of it, use local_flush_tlb_kernel_range which are available
> by more architectures. It would be better than supporting only x86
> and last patch in series will enable again with supporting
> local_flush_tlb_kernel_range in x86.
> 
> About local_flush_tlb_kernel_range,
> If architecture is very smart, it could flush only tlb entries related to vaddr.
> If architecture is smart, it could flush only tlb entries related to a CPU.
> If architecture is _NOT_ smart, it could flush all entries of all CPUs.
> So, it would be best to support both portability and performance.
> 
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Mundt <lethal@linux-sh.org>
> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
> Cc: Chen Liqin <liqin.chen@sunplusct.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> 
> Need double check about supporting local_flush_tlb_kernel_range
> in ARM, MIPS, SUPERH maintainers. And I will Ccing unicore32 and
> score maintainers because arch directory in those arch have
> local_flush_tlb_kernel_range, too but I'm very unfamiliar with those
> architecture so pass it to maintainers.
> I didn't coded up dumb local_flush_tlb_kernel_range which flush
> all cpus. I expect someone need ZSMALLOC will implement it easily in future.
> Seth might support it in PowerPC. :)
> 
> 
>  drivers/staging/zsmalloc/Kconfig         |    6 ++---
>  drivers/staging/zsmalloc/zsmalloc-main.c |   36 +++++++++++++++++++++---------
>  drivers/staging/zsmalloc/zsmalloc_int.h  |    1 -
>  3 files changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
> index a5ab720..def2483 100644
> --- a/drivers/staging/zsmalloc/Kconfig
> +++ b/drivers/staging/zsmalloc/Kconfig
> @@ -1,9 +1,9 @@
>  config ZSMALLOC
>  	tristate "Memory allocator for compressed pages"
> -	# X86 dependency is because of the use of __flush_tlb_one and set_pte
> +	# arch dependency is because of the use of local_unmap_kernel_range
>  	# in zsmalloc-main.c.
> -	# TODO: convert these to portable functions
> -	depends on X86
> +	# TODO: implement local_unmap_kernel_range in all architecture.
> +	depends on (ARM || MIPS || SUPERH)
I suggest removing above line, so if I want to use zsmalloc, I could
enable this configuration easily.

>  	default n
>  	help
>  	  zsmalloc is a slab-based memory allocator designed to store
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index 4496737..8a8b08f 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -442,7 +442,7 @@ static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
>  		area = &per_cpu(zs_map_area, cpu);
>  		if (area->vm)
>  			break;
> -		area->vm = alloc_vm_area(2 * PAGE_SIZE, area->vm_ptes);
> +		area->vm = alloc_vm_area(2 * PAGE_SIZE, NULL);
>  		if (!area->vm)
>  			return notifier_from_errno(-ENOMEM);
>  		break;
> @@ -696,13 +696,22 @@ void *zs_map_object(struct zs_pool *pool, void *handle)
>  	} else {
>  		/* this object spans two pages */
>  		struct page *nextp;
> +		struct page *pages[2];
> +		struct page **page_array = &pages[0];
> +		int err;
>  
>  		nextp = get_next_page(page);
>  		BUG_ON(!nextp);
>  
> +		page_array[0] = page;
> +		page_array[1] = nextp;
>  
> -		set_pte(area->vm_ptes[0], mk_pte(page, PAGE_KERNEL));
> -		set_pte(area->vm_ptes[1], mk_pte(nextp, PAGE_KERNEL));
> +		/*
> +		 * map_vm_area never fail because we already allocated
> +		 * pages for page table in alloc_vm_area.
> +		 */
> +		err = map_vm_area(area->vm, PAGE_KERNEL, &page_array);
> +		BUG_ON(err);
I think WARN_ON() is better than BUG_ON() here.

>  
>  		/* We pre-allocated VM area so mapping can never fail */
>  		area->vm_addr = area->vm->addr;
> @@ -712,6 +721,15 @@ void *zs_map_object(struct zs_pool *pool, void *handle)
>  }
>  EXPORT_SYMBOL_GPL(zs_map_object);
>  
> +static void local_unmap_kernel_range(unsigned long addr, unsigned long size)
> +{
> +	unsigned long end = addr + size;
> +
> +	flush_cache_vunmap(addr, end);
> +	unmap_kernel_range_noflush(addr, size);
> +	local_flush_tlb_kernel_range(addr, end);
> +}
> +
>  void zs_unmap_object(struct zs_pool *pool, void *handle)
>  {
>  	struct page *page;
> @@ -730,14 +748,12 @@ void zs_unmap_object(struct zs_pool *pool, void *handle)
>  	off = obj_idx_to_offset(page, obj_idx, class->size);
>  
>  	area = &__get_cpu_var(zs_map_area);
> -	if (off + class->size <= PAGE_SIZE) {
> +	if (off + class->size <= PAGE_SIZE)
>  		kunmap_atomic(area->vm_addr);
> -	} else {
> -		set_pte(area->vm_ptes[0], __pte(0));
> -		set_pte(area->vm_ptes[1], __pte(0));
> -		__flush_tlb_one((unsigned long)area->vm_addr);
> -		__flush_tlb_one((unsigned long)area->vm_addr + PAGE_SIZE);
> -	}
> +	else
> +		local_unmap_kernel_range((unsigned long)area->vm->addr,
> +					PAGE_SIZE * 2);
> +
>  	put_cpu_var(zs_map_area);
>  }
>  EXPORT_SYMBOL_GPL(zs_unmap_object);
> diff --git a/drivers/staging/zsmalloc/zsmalloc_int.h b/drivers/staging/zsmalloc/zsmalloc_int.h
> index 6fd32a9..eaec845 100644
> --- a/drivers/staging/zsmalloc/zsmalloc_int.h
> +++ b/drivers/staging/zsmalloc/zsmalloc_int.h
> @@ -111,7 +111,6 @@ static const int fullness_threshold_frac = 4;
>  
>  struct mapping_area {
>  	struct vm_struct *vm;
> -	pte_t *vm_ptes[2];
>  	char *vm_addr;
>  };
>  


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