Re: [PATCH 3/4] writeback: nr_dirtied and nr_entered_writeback in /proc/vmstat
From: Michael Rubin
Date: Fri Aug 20 2010 - 19:52:07 EST
On Fri, Aug 20, 2010 at 3:08 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> How about the names nr_dirty_accumulated and nr_writeback_accumulated?
> It seems more consistent, for both the interface and code (see below).
> I'm not really sure though.
Those names don't seem to right to me.
I admit I like "nr_dirtied" and "nr_cleaned" that seems most
understood. These numbers also get very big pretty fast so I don't
think it's hard to infer.
>> In order to track the "cleaned" and "dirtied" counts we added two
>> vm_stat_items. Per memory node stats have been added also. So we can
>> see per node granularity:
>>
>> # cat /sys/devices/system/node/node20/writebackstat
>> Node 20 pages_writeback: 0 times
>> Node 20 pages_dirtied: 0 times
>
> I'd prefer the name "vmstat" over "writebackstat", and propose to
> migrate items from /proc/zoneinfo over time. zoneinfo is a terrible
> interface for scripting.
I like vmstat also. I can do that.
> Also, are there meaningful usage of per-node writeback stats?
For us yes. We use fake numa nodes to implement cgroup memory isolation.
This allows us to see what the writeback behaviour is like per cgroup.
> The numbers are naturally per-bdi ones instead. But if we plan to
> expose them for each bdi, this patch will need to be implemented
> vastly differently.
Currently I have no plans to do that.
mrubin
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