Messages in this thread | | | Date | Thu, 3 Dec 2015 18:22:27 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64: calculate the various pages number to show |
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On Fri, Nov 27, 2015 at 09:52:16AM +0800, Xishi Qiu wrote: > On 2015/11/26 23:49, Mark Rutland wrote: > > > On Thu, Nov 26, 2015 at 11:05:32PM +0800, zhong jiang wrote: > >> On 2015/11/25 23:04, Mark Rutland wrote: > >>> On Wed, Nov 25, 2015 at 09:41:12PM +0800, zhongjiang wrote: > >>>> This patch add the interface to show the number of 4KB or 64KB page, > >>>> aims to statistics the number of different types of pages. > >>> > >>> What is this useful for? Why do we want it? > >>> > >>> What does it account for, just the swapper? > >>> > >> > >> The patch is wirtten when I was in backport set_memory_ro. It can be used to > >> detect whether there is a large page spliting and merging. large page will > >> significantly reduce the TLB miss, and improve the system performance. > > > > Ok, but typically the user isn't going to be able to do much with this > > information. It feels more like something that should be in the page > > table dump code (where we can calculate the values as we walk the > > tables). > > > > What is it intended to account for? > > > > The entire swapper? > > > > Just the linear mapping? > > Hi Mark, > > x86 has this information when cat /proc/meminfo, so how about just > like x86 to show it?
The fact that another architecture has some implementation doesn't necessarily mean it's a good idea. In this case there are concerns that don't apply to x86, in that we support a number of page sizes, and anything reading this needs to handle that fact.
If there's a sensible use-case, then I am not opposed to this. I don't see the point in adding it just because we can.
A prerequisite for adding it is knowing precisely what it is intended to describe. Otherwise it's impossible to review.
Thanks, Mark.
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