Re: [PATCH] mm: make mem_map allocation continuous.

[Ingo Molnar]

* Yinghai Lu <yhlu.kernel@xxxxxxxxx> wrote:

> [PATCH] mm: make mem_map allocation continuous.
> 
> vmemmap allocation current got
>  [ffffe20000000000-ffffe200001fffff] PMD ->ffff810001400000 on node 0
>  [ffffe20000200000-ffffe200003fffff] PMD ->ffff810001800000 on node 0
>  [ffffe20000400000-ffffe200005fffff] PMD ->ffff810001c00000 on node 0
>  [ffffe20000600000-ffffe200007fffff] PMD ->ffff810002000000 on node 0
>  [ffffe20000800000-ffffe200009fffff] PMD ->ffff810002400000 on node 0
> ...
> 
> there is 2M hole between them.
> 
> the rootcause is that usemap (24 bytes) will be allocated after every 2M
> mem_map. and it will push next vmemmap (2M) to next align (2M).
> 
> solution:
> try to allocate mem_map continously.
> 
> after patch, will get
>  [ffffe20000000000-ffffe200001fffff] PMD ->ffff810001400000 on node 0
>  [ffffe20000200000-ffffe200003fffff] PMD ->ffff810001600000 on node 0
>  [ffffe20000400000-ffffe200005fffff] PMD ->ffff810001800000 on node 0
>  [ffffe20000600000-ffffe200007fffff] PMD ->ffff810001a00000 on node 0
>  [ffffe20000800000-ffffe200009fffff] PMD ->ffff810001c00000 on node 0
> ...
> and usemap will share in page because of they are allocated continuously too.
> sparse_early_usemap_alloc: usemap = ffff810024e00000 size = 24
> sparse_early_usemap_alloc: usemap = ffff810024e00080 size = 24
> sparse_early_usemap_alloc: usemap = ffff810024e00100 size = 24
> sparse_early_usemap_alloc: usemap = ffff810024e00180 size = 24
> ...
> 
> so we make the bootmem allocation more compact and use less memory for usemap.
> 
> Signed-off-by: Yinghai Lu <yhlu.kernel@xxxxxxxxx>

very nice fix!

i suspect this patch should go via -mm.

>  	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
> +	printk(KERN_INFO "sparse_early_usemap_alloc: usemap = %p size = %ld\n", usemap, usemap_size());

this should be in a separate patch.

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/