Re: [PATCH RFC] mm, proc: add PcpFree to meminfo

[Kefeng Wang]

On 2022/8/16 17:16, Greg Kroah-Hartman wrote:
> On Tue, Aug 16, 2022 at 04:44:26PM +0800, Kefeng Wang wrote:
> > From: Liu Shixin <liushixin2@xxxxxxxxxx>
> >
> > The page on pcplist could be used, but not counted into memory free or
> > avaliable, and pcp_free is only showed by show_mem(). Since commit
> > d8a759b57035 ("mm, page_alloc: double zone's batchsize"), there is a
> > significant decrease in the display of free memory, with a large number
> > of cpus and nodes, the number of pages in the percpu list can be very
> > large, so it is better to let user to know the pcp count.
> >
> > Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
> > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > ---
> >   drivers/base/node.c | 14 +++++++++++++-
> >   fs/proc/meminfo.c   |  9 +++++++++
> >   2 files changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/node.c b/drivers/base/node.c
> > index eb0f43784c2b..846864e45db6 100644
> > --- a/drivers/base/node.c
> > +++ b/drivers/base/node.c
> > @@ -375,6 +375,9 @@ static ssize_t node_read_meminfo(struct device *dev,
> >   	struct sysinfo i;
> >   	unsigned long sreclaimable, sunreclaimable;
> >   	unsigned long swapcached = 0;
> > +	unsigned long free_pcp = 0;
> > +	struct zone *zone;
> > +	int cpu;
> >   
> >   	si_meminfo_node(&i, nid);
> >   	sreclaimable = node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B);
> > @@ -382,9 +385,17 @@ static ssize_t node_read_meminfo(struct device *dev,
> >   #ifdef CONFIG_SWAP
> >   	swapcached = node_page_state_pages(pgdat, NR_SWAPCACHE);
> >   #endif
> > +	for_each_populated_zone(zone) {
> > +		if (zone_to_nid(zone) != nid)
> > +			continue;
> > +		for_each_online_cpu(cpu)
> > +			free_pcp += per_cpu_ptr(zone->per_cpu_pageset, cpu)->count;
> > +	}
> > +
> >   	len = sysfs_emit_at(buf, len,
> >   			    "Node %d MemTotal:       %8lu kB\n"
> >   			    "Node %d MemFree:        %8lu kB\n"
> > +			    "Node %d PcpFree:        %8lu kB\n"
> First off, this sysfs file is a huge violation of the normal sysfs
> rules, so I will not allow any new entries to be added.  In fact, the
> whole thing should just be removed and multiple files created in its
> place.

Hi Greg, do you mean to remove all /sys/devices/system/node/node*/meminfo,

but this will beak ABI, is it acceptable?

> Can you send a patch to do that instead please?
>
> thanks,
>
> greg k-h
> .