Hello, 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 > > > this. > > > > 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 > net-fix-functions-and-variables-related-to-netns_ipvs-sysctl_sync_qlen_max.patch > are joined at the hip and should be redone as a single patch with a > suitable changelog, please. And with a cc:netdev@xxxxxxxxxxxxxxx. 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. Regards -- Julian Anastasov <ja@xxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>