From 44b308531e8c1823ecdcad17488c4e5eea36c19a Mon Sep 17 00:00:00 2001 From: Thomas Schwinge Date: Sat, 8 Jan 2011 00:47:56 +0100 Subject: open_issues/mach_tasks_memory_usage: New. IRC, #hurd, 2011-01-06. --- open_issues/mach_tasks_memory_usage.mdwn | 100 +++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) create mode 100644 open_issues/mach_tasks_memory_usage.mdwn (limited to 'open_issues') diff --git a/open_issues/mach_tasks_memory_usage.mdwn b/open_issues/mach_tasks_memory_usage.mdwn new file mode 100644 index 00000000..12758dbc --- /dev/null +++ b/open_issues/mach_tasks_memory_usage.mdwn @@ -0,0 +1,100 @@ +[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_documentation]] + +IRC, #hurd, 2011-01-06. + + hm, odd... vmstat tells me that ~500 MiB of RAM are in use; but + the sum of all RSS is <300 MiB... what's the rest? + kernel memory ? + the zone allocator maybe + or the page cache simply + braunr: which page cache? AIUI, caches are implemented by the + individual filesystem servers -- in which case any memory used by them + should show up in RSS + also, gnumach is listed among other tasks, so I'd assume the + kernel memery also to be accounted for + antrik: no, the kernel maintains a page cache, very similar to + what is done in Linux, and almost the same as in FreeBSD + the file system servers are just backing stores + the RSS for the gnumach tasks only includes kernel memory + I don't think the page cache is accounted for + because it's not really kernel memory, it's a cache of user space + memory + apparently my understanding of Mach paging is still (or again?) + rather incomplete :-( + BTW, is there any way to find out how much anonymous memory a + process is using? the "virtual" includes discardable mappings, and is + thus not very helpful... + (that applies to Linux as well though) + can you provide an example of the output of vmstat please ? + I don't have a Hurd VM near me + olaf@alien:~$ vmstat + pagesize: 4K + size: 501M + free: 6.39M + active: 155M + inactive: 310M + wired: 29.4M + zero filled: 15.3G + reactivated: 708M + pageins: 3.43G + pageouts: 1.55G + page faults: 26844574 + cow faults: 3736174 + memobj hit ratio: 92% + swap size: 733M + swap free: 432M + interesting... closing a single screen window temporarily raises + the "free" value by almost 10 MB + I guess bash is rather hungry nowadays ;-) + antrik: I guess the only way is using pmap or looking into + /proc//maps + but it won't give you the amount of physical memory used by + anonymous mappings + nah, I don't even want that... just like to know how much memory + (RAM+swap) a process is really using + antrik: then the RSS field is what you want + OTOH, anonymous doesn't include program code or other actively + used mappings... so not very useful either + nah, RSS doesn't count anything that is in swap + well + don't you have a SWAP column ? + hm + i guess not + antrik: why do you say it doesn't include other actively used + mappings ? + antrik: and the inclusion of program code also depends on the + implementation of the ELF handler + I don't know how the hurd does that, but some ELF loaders use + anonymous memory for the execution view + well, if a program maps a data file, and regularily accesses parts + of the file, they won't occupy physical RAM all the time (and show up in + RSS), but they are not anonymous mappings. similar to program code + then this anonymous memory is shared by all processes using that + code + oh, interesting + is it really a completely distinct mapping, rather than just COW? + the first is + others are COW + so if a program loads 200 MB of libraries, they are all read in on + startup, and occupy RAM or swap subsequently, even if most of the code is + never actually run?... + library code should be backed by the library file on disk, not be + swap + depends on the implementation + I guess most use the file system backend + but in the Hurd, ext2fs.static and ld.so.1 use anonymous memory + (that's the case for another reason, still, I don't think the + report in top/ps clearly indicates that fact) + braunr: yeah for bootstrapping issues, makes sense + it may also depends on the pic/pie options used when building + libraries -- cgit v1.2.3