Messages in this thread |  | | | Subject | Re: Better pagecache statistics ? | | From | Badari Pulavarty <> | | Date | Fri, 02 Dec 2005 14:31:56 -0800 |
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On Fri, 2005-12-02 at 17:15 -0500, Frank Ch. Eigler wrote: > Badari Pulavarty <pbadari@us.ibm.com> writes: > > > > Can't you add hooks to add_to_page_cache/remove_from_page_cache > > > to record pagecache activity ? > > > > In theory, yes. We already maintain info in "mapping->nrpages". > > Trick would be to collect all of them, send them to user space. > > If you happened to have a copy of systemtap built, you might run this > script instead of inserting static hooks into your kernel. (The tool > has come some way since the OLS '2005 demo.) > > #! stap > probe kernel.function("add_to_page_cache") { > printf("pid %d added pages (%d)\n", pid(), $mapping->nrpages) > } > probe kernel.function("__remove_from_page_cache") { > printf("pid %d removed pages (%d)\n", pid(), $page->mapping->nrpages) > }
Yes. This is what I also did earlier to test. But unfortunately, we need more than this.
Having by "pid" basis is not good enough. I need per file/mapping basis collected and sent to user-space on-demand. Is systemtap hooked to relayfs to send data across to user-land ? printf() is not an option. And also, I need to have this probe, installed from the boot time and collecting all the information - so I can access it when I need it - which means this bloats kernel memory. Isn't it ?
Thanks, Badari
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