Re: [PATCH v3] mlx4_core: allocate ICM memory in page size chunks

[Qing Huang]

On 5/17/2018 2:14 PM, Eric Dumazet wrote:
> On 05/17/2018 01:53 PM, Qing Huang wrote:
> > When a system is under memory presure (high usage with fragments),
> > the original 256KB ICM chunk allocations will likely trigger kernel
> > memory management to enter slow path doing memory compact/migration
> > ops in order to complete high order memory allocations.
> >
> > When that happens, user processes calling uverb APIs may get stuck
> > for more than 120s easily even though there are a lot of free pages
> > in smaller chunks available in the system.
> >
> > Syslog:
> > ...
> > Dec 10 09:04:51 slcc03db02 kernel: [397078.572732] INFO: task
> > oracle_205573_e:205573 blocked for more than 120 seconds.
> > ...
> NACK on this patch.
>
> You have been asked repeatedly to use kvmalloc()
>
> This is not a minor suggestion.
>
> Take a look athttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d8c13f2271ec5178c52fbde072ec7b562651ed9d

Would you please take a look at how table->icm is being used in the mlx4 
driver? It's a meta data used for individual pointer variable referencing,
not as data frag or in/out buffer. It has no need for contiguous phy. 
memory.

Thanks.

> And you'll understand some people care about this.
>
> Strongly.
>
> Thanks.