Re: [PATCH 1/4] xvmalloc memory allocator

Nitin Gupta
2009-09-22T03:51:40Z

Sorry for late reply. I nearly missed this mail. My comments inline.

On 09/19/2009 02:35 AM, Marcin Slusarz wrote:
> Nitin Gupta wrote:
>> (...)
>> +
>> +/*
>> + * Allocate a memory page. Called when a pool needs to grow.
>> + */
>> +static struct page *xv_alloc_page(gfp_t flags)
>> +{
>> + struct page *page;
>> +
>> + page = alloc_page(flags);
>> + if (unlikely(!page))
>> + return 0;
>> +
>> + return page;
>> +}
>
> When alloc_page returns 0 it returns 0, when not - it returns page.
> Why not call alloc_page directly?
>

We now call alloc_page() and __free_page directly. Removed these wrappers.

>> (...)
>> +/*
>> + * Remove block from freelist. Index 'slindex' identifies the freelist.
>> + */
>> +static void remove_block(struct xv_pool *pool, struct page *page, u32 offset,
>> + struct block_header *block, u32 slindex)
>> +{
>> + u32 flindex;
>> + struct block_header *tmpblock;
<snip>
>> +
>> + return;
>> +}
>
> needless return
>

Removed.

>> +int xv_malloc(struct xv_pool *pool, u32 size, struct page **page,
>> + u32 *offset, gfp_t flags)
>> +{
>> + int error;
>> +
<snip>
>> + if (!*page) {
>> + spin_unlock(&pool->lock);
>> + if (flags & GFP_NOWAIT)
>> + return -ENOMEM;
>> + error = grow_pool(pool, flags);
>> + if (unlikely(error))
>> + return -ENOMEM;
>
> shouldn't it return error? (grow_pool returns 0 or -ENOMEM for now but...)
>

Yes, it should return error. Corrected.

>> +
>> + spin_lock(&pool->lock);
>> + index = find_block(pool, size, page, offset);
>> + }
>> +
>> + if (!*page) {
>> + spin_unlock(&pool->lock);
>> + return -ENOMEM;
>> + }
>> +
>> + block = get_ptr_atomic(*page, *offset, KM_USER0);
>> +
>> + remove_block_head(pool, block, index);
>> +
>> + /* Split the block if required */
>> + tmpoffset = *offset + size + XV_ALIGN;
>> + tmpsize = block->size - size;
>> + tmpblock = (struct block_header *)((char *)block + size + XV_ALIGN);
>> + if (tmpsize) {
>> + tmpblock->size = tmpsize - XV_ALIGN;
>> + set_flag(tmpblock, BLOCK_FREE);
>> + clear_flag(tmpblock, PREV_FREE);
>> +
>> + set_blockprev(tmpblock, *offset);
>> + if (tmpblock->size >= XV_MIN_ALLOC_SIZE)
>> + insert_block(pool, *page, tmpoffset, tmpblock);
>> +
>> + if (tmpoffset + XV_ALIGN + tmpblock->size != PAGE_SIZE) {
>> + tmpblock = BLOCK_NEXT(tmpblock);
>> + set_blockprev(tmpblock, tmpoffset);
>> + }
>> + } else {
>> + /* This block is exact fit */
>> + if (tmpoffset != PAGE_SIZE)
>> + clear_flag(tmpblock, PREV_FREE);
>> + }
>> +
>> + block->size = origsize;
>> + clear_flag(block, BLOCK_FREE);
>> +
>> + put_ptr_atomic(block, KM_USER0);
>> + spin_unlock(&pool->lock);
>> +
>> + *offset += XV_ALIGN;
>> +
>> + return 0;
>> +}
>> +
>> +/*
>> + * Free block identified with <page, offset>
>> + */
>> +void xv_free(struct xv_pool *pool, struct page *page, u32 offset)
>> +{
<snip>
>> + return;
>> +}
>
> needless return
>
>

Removed.

Regarding your comments on page_zero_filled: I'm not sure if using unsigned
long is better or just u64 irrespective of arch. I just changed it to ulong
-- some bechmarks can help decide which one is optimal. Maybe we need arch
specific optimized versions which means moving it to lib/ or something.

Thanks for your feedback.

Nitin