Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 2/3] vmscan: make mapped executable pages the first class citizen | Date | Wed, 20 May 2009 10:59:05 +0900 (JST) |
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> On Tue, May 19, 2009 at 08:28:28PM +0800, KOSAKI Motohiro wrote: > > Hi > > > > 2009/5/19 Wu Fengguang <fengguang.wu@intel.com>: > > > On Tue, May 19, 2009 at 04:06:35PM +0800, KOSAKI Motohiro wrote: > > >> > > > Like the console mode, the absolute nr_mapped drops considerably - to 1/13 of > > >> > > > the original size - during the streaming IO. > > >> > > > > > >> > > > The delta of pgmajfault is 3 vs 107 during IO, or 236 vs 393 during the whole > > >> > > > process. > > >> > > > > >> > > hmmm. > > >> > > > > >> > > about 100 page fault don't match Elladan's problem, I think. > > >> > > perhaps We missed any addional reproduce condition? > > >> > > > >> > Elladan's case is not the point of this test. > > >> > Elladan's IO is use-once, so probably not a caching problem at all. > > >> > > > >> > This test case is specifically devised to confirm whether this patch > > >> > works as expected. Conclusion: it is. > > >> > > >> Dejection ;-) > > >> > > >> The number should address the patch is useful or not. confirming as expected > > >> is not so great. > > > > > > OK, let's make the conclusion in this way: > > > > > > The changelog analyzed the possible beneficial situation, and this > > > test backs that theory with real numbers, ie: it successfully stops > > > major faults when the active file list is slowly scanned when there > > > are partially cache hot streaming IO. > > > > > > Another (amazing) finding of the test is, only around 1/10 mapped pages > > > are actively referenced in the absence of user activities. > > > > > > Shall we protect the remaining 9/10 inactive ones? This is a question ;-) > > > > Unfortunately, I don't reproduce again. > > I don't apply your patch yet. but mapped ratio is reduced only very little. > > mapped ratio or absolute numbers? The ratio wont change much because > nr_mapped is already small.
My box is running Fedora 10 initlevel 5 (GNOME desktop).
many GNOME component is mapped very many process (likes >50). Thus, these page aren't dropped by typical any workload.
> > I think smem can show which library evicted. Can you try it? > > > > download: http://www.selenic.com/smem/ > > usage: ./smem -m -r --abbreviate > > Sure, but I don't see much change in its output (see attachments). > > smem-console-0 is collected after fresh boot, > smem-console-1 is collected after the big IO.
hmmmm, your result has following characatistics.
- no graphics component - very few mapped library (it is almost only zsh library)
Can you try test on X environment?
> > We can't decide 9/10 is important or not. we need know actual evicted file list. > > Right. But what I measured is the activeness. Almost zero major page > faults means the evicted 90% mapped pages are inactive during the > long 300 seconds of IO.
Agreed. IOW, I don't think your test environment is typical desktop...
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