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Date: Thu, 17 May 2012 09:07:35 +0900
From: Minchan Kim <minchan@...nel.org>
To: Guan Xuetao <gxt@...c.pku.edu.cn>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Nitin Gupta <ngupta@...are.org>,
Seth Jennings <sjenning@...ux.vnet.ibm.com>,
Dan Magenheimer <dan.magenheimer@...cle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Russell King <linux@....linux.org.uk>,
Ralf Baechle <ralf@...ux-mips.org>,
Paul Mundt <lethal@...ux-sh.org>,
Chen Liqin <liqin.chen@...plusct.com>
Subject: Re: [PATCH v2 1/3] zsmalloc: support zsmalloc to ARM, MIPS, SUPERH
On 05/16/2012 04:28 PM, Guan Xuetao wrote:
> 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@....linux.org.uk>
>> Cc: Ralf Baechle <ralf@...ux-mips.org>
>> Cc: Paul Mundt <lethal@...ux-sh.org>
>> Cc: Guan Xuetao <gxt@...c.pku.edu.cn>
>> Cc: Chen Liqin <liqin.chen@...plusct.com>
>> Signed-off-by: Minchan Kim <minchan@...nel.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.
I don't get it. What do you mean?
If I remove above line, compile error will happen if arch doesn't support local_unmap_kernel_range.
>
>> 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.
If we don't do BUG_ON, zsmalloc's user can use dangling pointer so that it can make system very
unstable, even fatal.
>
>>
>> /* 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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--
Kind regards,
Minchan Kim
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