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

On 18/05/2018 12:45 AM, Qing Huang wrote:

On 5/17/2018 2:14 PM, Eric Dumazet wrote:

quoted

On 05/17/2018 01:53 PM, Qing Huang wrote:

quoted

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.

NACK.

This would cause a degradation when iterating the entries of table->icm.
For example, in mlx4_table_get_range.

Thanks,
Tariq

quoted

And you'll understand some people care about this.

Strongly.

Thanks.