Re: [PATCH v2] net: fix functions and variables related to netns_ipvs->sysctl_sync_qlen_max
From: Zhang Yanfei
Date: Mon Feb 18 2013 - 01:18:34 EST
ä 2013å02æ16æ 05:39, Julian Anastasov åé:
> On Thu, 14 Feb 2013, Andrew Morton wrote:
>> On Thu, 7 Feb 2013 10:40:26 +0200 (EET)
>> Julian Anastasov <ja@xxxxxx> wrote:
>>>> Another question about the sysctl_sync_qlen_max:
>>>> This variable is assigned as:
>>>> ipvs->sysctl_sync_qlen_max = nr_free_buffer_pages() / 32;
>>>> The function nr_free_buffer_pages actually means: counts of pages
>>>> which are beyond high watermark within ZONE_DMA and ZONE_NORMAL.
>>>> is it ok to be called here? Some people misused this function because
>>>> the function name was misleading them. I am sorry I am totally not
>>>> familiar with the ipvs code, so I am just asking you about
>>> Using nr_free_buffer_pages should be fine here.
>>> We are using it as rough estimation for the number of sync
>>> buffers we can use in NORMAL zones. We are using dev->mtu
>>> for such buffers, so it can take a PAGE_SIZE for a buffer.
>>> We are not interested in HIGHMEM size. high watermarks
>>> should have negliable effect. I'm even not sure whether
>>> we need to clamp it for systems with TBs of memory.
>> Using nr_free_buffer_pages() is good-enough-for-now. There are
>> questions around the name of this thing and its exact functionality and
>> whether callers are using it appropriately. But if anything is changed
>> there, it will be as part of kernel-wide sweep.
>> One thing to bear in mind is memory hot[un]plug. Anything which was
>> sized using nr_free_buffer_pages() (or similar) may become
>> inappropriately sized if memory is added or removed. So any site which
>> uses nr_free_buffer_pages() really should be associated with a hotplug
>> handler and a great pile of code to resize the structure at runtime.
>> It's pretty ugly stuff :( I suspect it usually Just Doesn't Matter.
> I'll try to think on this hotplug problem
> and also on the si_meminfo usage in net/netfilter/ipvs/ip_vs_ctl.c
> which is quite wrong for systems with HIGHMEM, may be
> we need there a free+reclaimable+file function for
> NORMAL zone.
>> Redarding this patch:
>> net-change-type-of-netns_ipvs-sysctl_sync_qlen_max.patch and
>> are joined at the hip and should be redone as a single patch with a
>> suitable changelog, please. And with a cc:netdev@xxxxxxxxxxxxxxxx
> Agreed, Zhang Yanfei and Simon? I'm just not sure,
> may be this combined patch should hit only the
> ipvs->nf->net trees? Or may be net-next, if we don't have
> time for 3.8.
Should I resend the combined patch?
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