Re: [PATCH v3 02/12] sched: remove a wake_affine condition

[Rik van Riel]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 06/30/2014 12:05 PM, Vincent Guittot wrote:
> I have tried to understand the meaning of the condition : 
> (this_load <= load && this_load + target_load(prev_cpu, idx) <=
> tl_per_task) but i failed to find a use case that can take
> advantage of it and i haven't found clear description in the
> previous commits' log. Futhermore, the comment of the condition
> refers to the task_hot function that was used before being replaced
> by the current condition: /* * This domain has SD_WAKE_AFFINE and *
> p is cache cold in this domain, and * there is no bad imbalance. 
> */
> 
> If we look more deeply the below condition this_load +
> target_load(prev_cpu, idx) <= tl_per_task
> 
> When sync is clear, we have : tl_per_task = runnable_load_avg /
> nr_running this_load = max(runnable_load_avg, cpuload[idx]) 
> target_load =  max(runnable_load_avg', cpuload'[idx])
> 
> It implies that runnable_load_avg' == 0 and nr_running <= 1 in
> order to match the condition. This implies that runnable_load_avg
> == 0 too because of the condition: this_load <= load but if this
> _load is null, balanced is already set and the test is redundant.
> 
> If sync is set, it's not as straight forward as above (especially
> if cgroup are involved) but the policy should be similar as we have
> removed a task that's going to sleep in order to get a more
> accurate load and this_load values.
> 
> The current conclusion is that these additional condition don't
> give any benefit so we can remove them.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

- -- 
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/

iQEcBAEBAgAGBQJTvLG+AAoJEM553pKExN6DfhMH/iYJAS/nCq1teCNm39zZg1bF
MIp2iWwnB5VTQvwVLQ3FaGU80oWScUez8zjn26LjPp5SnxyDEwG0YVM3/57EyJme
PgffmP8xsVJwRkKnO4VRR0Go2EMXl9cdf9exe6lFjRyv4/Z15o9NZsDmX8JcLmG+
JPKq4DnMpJ3LiMiVuwwYtYSLk/tCHCPLnie4Z/WznlHk220WciVXFZG7AQI2AHXj
pMkZ5TWQODW7PEec+8dGzDnFcdXPftRYWCKLXG+9NM92YQpIsK8nZdC8rJeXhjBC
9VNb8QNZ6yVd0lvOSxy0drOV9BFXUImF6lsLxA12oHE6TLm6FeiHTG9X4xGOhN0=
=XlY9
-----END PGP SIGNATURE-----
--
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/