lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 25 Jul 2014 17:02:12 +0200
From:	Vincent Guittot <>
To:	Rik van Riel <>
Cc:	linux-kernel <>,
	Peter Zijlstra <>,
	Michael Neuling <>,
	Ingo Molnar <>, Paul Turner <>,,,,
	Nicolas Pitre <>
Subject: Re: [PATCH] sched: make update_sd_pick_busiest return true on a
 busier sd

On 25 July 2014 16:02, Rik van Riel <> wrote:
> Hash: SHA1
> On 07/23/2014 03:41 AM, Vincent Guittot wrote:
>> Regarding your issue with "perf bench numa mem" that is not spread
>> on all nodes, SD_PREFER_SIBLING flag (of DIE level) should do the
>> job by reducing the capacity of  "not local DIE" group at NUMA
>> level to 1 task during the load balance computation. So you should
>> have 1 task per sched_group at NUMA level.
> Looking at the code some more, it is clear why this does not
> happen. If sd->flags & SD_NUMA, then SD_PREFER_SIBLING will
> never be set.

I don't have a lot of experience on NUMA system and how their
sched_domain topology is described but IIUC, you don't have other
sched_domain level than NUMA ones ? otherwise the flag should be
present in one of the non NUMA level (SMT, MC or DIE)

> On a related note, that part of the load balancing code probably
> needs to be rewritten to deal with unequal group_capacity_factors
> anyway.
> Say that one group has a group_capacity_factor twice that of
> another group.
> The group with the smaller group_capacity_factor is overloaded
> by a factor 1.3. The larger group is loaded by a factor 0.8.
> This means the larger group has a higher load than the first
> group, and the current code in update_sd_pick_busiest will
> not select the overloaded group as the busiest one, due to not
> scaling load with the capacity...

AFAICT, sgs->avg_load is weighted by the capacity in update_sg_lb_stats

> static bool update_sd_pick_busiest(struct lb_env *env,
>                                    struct sd_lb_stats *sds,
>                                    struct sched_group *sg,
>                                    struct sg_lb_stats *sgs)
> {
>         if (sgs->avg_load <= sds->busiest_stat.avg_load)
>                 return false;
> I believe we may need to factor the group_capacity_factor
> into this calculation, in order to properly identify which
> group is busiest.
> However, if we do that we may need to get rid of the
> SD_PREFER_SIBLING hack that forces group_capacity_factor
> to 1 on domains that have SD_PREFER_SIBLING set.

I'm working on a patchset that get ride of capacity_factor (as
mentioned by Peter) and directly uses capacity instead. I should send
the v4 next week.

> I suspect that should be ok though, if we make sure
> update_sd_pick_busiest does the right thing...
> - --
> All rights reversed
> Version: GnuPG v1
> Comment: Using GnuPG with Thunderbird -
> HATAp8Dv0kTiGjnbZrHPp8TqqgLLXuM6HhLvsvURuhoJw6F/nOX6qOQWEtjcMyYp
> omShkDSLnPjs/0Iwf9vNocT7K7Sn3Gk0hOj6+ICW7wchyug8JYtuiHunP8pYrpzW
> G6l2qHMRqRs5mSENY/uWwH9qh6Z6jcfDoDDDKRTNBe0z67FzwMnX1IYCUA6XOBsZ
> iRdXe8E0CIgio+ek8HVzRm5sUlkRyfJpTXJj+pemVJhTrNCCbMGTHxzADU4Ngc8S
> +JQ+G6bsHz9R4pffsuzYFbL0avK0mm5SrjCIatE7MX171dQJ1cKpju+fAmnwuNg=
> =EAzG
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists