On 01/11/2012 11:19 AM, Dan Magenheimer wrote:
>> From: Seth Jennings [mailto:[email protected]]
>> Subject: [PATCH 1/5] staging: zsmalloc: zsmalloc memory allocation library
>>
>> From: Nitin Gupta <[email protected]>
>>
>> This patch creates a new memory allocation library named
>> zsmalloc.
>>
>> +/*
>> + * Allocate a zspage for the given size class
>> + */
>> +static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
>> +{
>> +    int i, error;
>> +    struct page *first_page = NULL;
>> +
>> +    /*
>> +     * Allocate individual pages and link them together as:
>> +     * 1. first page->private = first sub-page
>> +     * 2. all sub-pages are linked together using page->lru
>> +     * 3. each sub-page is linked to the first page using page->first_page
>> +     *
>> +     * For each size class, First/Head pages are linked together using
>> +     * page->lru. Also, we set PG_private to identify the first page
>> +     * (i.e. no other sub-page has this flag set) and PG_private_2 to
>> +     * identify the last page.
>> +     */
>> +    error = -ENOMEM;
>> +    for (i = 0; i < class->zspage_order; i++) {
>> +            struct page *page, *prev_page;
>> +
>> +            page = alloc_page(flags);
> 
> Hmmm... I thought we agreed offlist that the new allocator API would
> provide for either preloads or callbacks (which may differ per pool)
> instead of directly allocating raw pages from the kernel.  The caller
> (zcache or ramster or ???) needs to be able to somehow manage maximum
> memory capacity to avoid OOMs.
> 
> Or am I missing the code that handles that?

No, you aren't missing it; it's not there.  And I agree that we
should add that.

However, the existing allocator, xvmalloc, doesn't support callback
functionality either.  Would it be simpler to add the that as 
a separate patch, that way we can keep the changes to zcache/zram
in this patchset isolated to just changing the xvmalloc calls to 
zsmalloc calls?

--
Seth

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