Re: [PATCH 7/9] net: use kvmalloc with __GFP_REPEAT rather than open coded variant

[Shakeel Butt]

On Mon, Mar 6, 2017 at 2:33 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> fq_alloc_node, alloc_netdev_mqs and netif_alloc* open code kmalloc
> with vmalloc fallback. Use the kvmalloc variant instead. Keep the
> __GFP_REPEAT flag based on explanation from Eric:
> "
> At the time, tests on the hardware I had in my labs showed that
> vmalloc() could deliver pages spread all over the memory and that was a
> small penalty (once memory is fragmented enough, not at boot time)
> "
>
> The way how the code is constructed means, however, that we prefer to go
> and hit the OOM killer before we fall back to the vmalloc for requests
> <=32kB (with 4kB pages) in the current code. This is rather disruptive for
> something that can be achived with the fallback. On the other hand
> __GFP_REPEAT doesn't have any useful semantic for these requests. So the
> effect of this patch is that requests smaller than 64kB will fallback to

I am a bit confused about this 64kB, shouldn't it be <=32kB (with 4kB
pages & PAGE_ALLOC_COSTLY_ORDER = 3)?

> vmalloc easier now.
>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---