Date: Fri, 19 Sep 2003 23:11:39 +0200 From: "Ralf S. Engelschall" <rse@engelschall.com> To: freebsd-hackers@freebsd.org Subject: Gaps in memory usage summary!? Message-ID: <20030919211138.GA67987@engelschall.com>
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--a8Wt8u1KmwUX3Y2C
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I'm trying to automate the summarization of memory usage on our
FreeBSD boxes with the attached little Perl program and have some
remaining questions I was not able to answer myself. When run on three
representing boxes (all -STABLE and -CURRENT as of yesterday) I get this
output:
------------------------------------------------------------------------------
FreeBSD-4.8-STABLE/i386
SYSTEM MEMORY INFORMATION:
mem_wire: 162615296 ( 155MB) [ 7%] Wired: disabled for paging out
mem_active: + 159956992 ( 152MB) [ 7%] Active: recently referenced
mem_inactive:+ 950210560 ( 906MB) [ 45%] Inactive: recently not referenced
mem_cache: + 75137024 ( 71MB) [ 3%] Cached: almost avail. for allocation
mem_free: + 759664640 ( 724MB) [ 36%] Free: fully available for allocation
mem_gap_vm: + 364544 ( 0MB) [ 0%] Memory gap: UNKNOWN
-------------- ------------ ----------- ------
mem_all: = 2107949056 ( 2010MB) [100%] Total real memory managed
mem_gap_sys: + 35684352 ( 34MB) Memory gap: Kernel?!
-------------- ------------ -----------
mem_phys: = 2143633408 ( 2044MB) Total real memory available
mem_gap_hw: + 3850240 ( 3MB) Memory gap: Segment Mappings?!
-------------- ------------ -----------
mem_hw: = -2147483648 ( 2048MB) Total real memory installed
SYSTEM MEMORY SUMMARY:
mem_used: 322936832 ( 307MB) [ 15%] Logically unused memory
mem_avail: + 1785012224 ( 1702MB) [ 84%] Logically available memory
-------------- ------------ ----------- ------
mem_total: = 2107949056 ( 2010MB) [100%] Logically total memory
------------------------------------------------------------------------------
FreeBSD-5.1-CURRENT/i386
SYSTEM MEMORY INFORMATION:
mem_wire: 136101888 ( 129MB) [ 12%] Wired: disabled for paging out
mem_active: + 187867136 ( 179MB) [ 17%] Active: recently referenced
mem_inactive:+ 648417280 ( 618MB) [ 61%] Inactive: recently not referenced
mem_cache: + 9150464 ( 8MB) [ 0%] Cached: almost avail. for allocation
mem_free: + 68550656 ( 65MB) [ 6%] Free: fully available for allocation
mem_gap_vm: + 0 ( 0MB) [ 0%] Memory gap: UNKNOWN
-------------- ------------ ----------- ------
mem_all: = 1050087424 ( 1001MB) [100%] Total real memory managed
mem_gap_sys: + 19030016 ( 18MB) Memory gap: Kernel?!
-------------- ------------ -----------
mem_phys: = 1069117440 ( 1019MB) Total real memory available
mem_gap_hw: + 4624384 ( 4MB) Memory gap: Segment Mappings?!
-------------- ------------ -----------
mem_hw: = 1073741824 ( 1024MB) Total real memory installed
SYSTEM MEMORY SUMMARY:
mem_used: 323969024 ( 308MB) [ 30%] Logically unused memory
mem_avail: + 726118400 ( 692MB) [ 69%] Logically available memory
-------------- ------------ ----------- ------
mem_total: = 1050087424 ( 1001MB) [100%] Logically total memory
------------------------------------------------------------------------------
FreeBSD-5.1-CURRENT/alpha
SYSTEM MEMORY INFORMATION:
mem_wire: 32555008 ( 31MB) [ 12%] Wired: disabled for paging out
mem_active: + 57344000 ( 54MB) [ 22%] Active: recently referenced
mem_inactive:+ 116170752 ( 110MB) [ 45%] Inactive: recently not referenced
mem_cache: + 4620288 ( 4MB) [ 1%] Cached: almost avail. for allocation
mem_free: + 12484608 ( 11MB) [ 4%] Free: fully available for allocation
mem_gap_vm: + 31113216 ( 29MB) [ 12%] Memory gap: UNKNOWN
-------------- ------------ ----------- ------
mem_all: = 254287872 ( 242MB) [100%] Total real memory managed
mem_gap_sys: + 11116544 ( 10MB) Memory gap: Kernel?!
-------------- ------------ -----------
mem_phys: = 265404416 ( 253MB) Total real memory available
mem_gap_hw: + 3031040 ( 2MB) Memory gap: Segment Mappings?!
-------------- ------------ -----------
mem_hw: = 268435456 ( 256MB) Total real memory installed
SYSTEM MEMORY SUMMARY:
mem_used: 121012224 ( 115MB) [ 47%] Logically unused memory
mem_avail: + 133275648 ( 127MB) [ 52%] Logically available memory
-------------- ------------ ----------- ------
mem_total: = 254287872 ( 242MB) [100%] Logically total memory
------------------------------------------------------------------------------
My remaining questions now are:
1. What memory is "map_gap_vm" and why is there no such gap on Intel
boxes but on Alpha boxes? The number I arithmetically calculate is
vm.stats.vm.v_page_count
- ( vm.stats.vm.v_wire_count
+ vm.stats.vm.v_active_count
+ vm.stats.vm.v_inactive_count
+ vm.stats.vm.v_cache_count
+ vm.stats.vm.v_free_count )
and I always would expect 0 here, but as you can see it is not at
least on Alpha. Is this a bug in our VM statistic code? Any clues?
2. What memory is "mem_gap_sys", i.e.
(hw.physmem - (vm.stats.vm.v_page_count * hw.pagesize)) ?
Is this the loaded kernel code?
3. What memory is "mem_gap_hw", i.e.
(rounded(hw.physmem) - hw.physmem) ?
Is this caused by some special hardware memory segmenting?
I would be happy if someone could shed some light on this. Thanks.
Ralf S. Engelschall
rse@engelschall.com
www.engelschall.com
--a8Wt8u1KmwUX3Y2C
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#!/usr/bin/perl
# query the system through the generic sysctl(8) interface
# (this does not require special priviledges)
my $sysctl = {};
my $sysctl_output = `/sbin/sysctl -a`;
foreach my $line (split(/\n/, $sysctl_output)) {
if ($line =~ m/^([^:]+):\s+(.+)\s*$/s) {
$sysctl->{$1} = $2;
}
}
# round the physical memory size to the next power of two which is
# reasonable for memory cards. We do this by first determining the
# guessed memory card size under the assumption that usual computer
# hardware has an average of a maximally eight memory cards installed
# and those are usually of equal size.
sub mem_rounded {
my ($mem_size) = @_;
my $chip_size = 1;
my $chip_guess = ($mem_size / 8) - 1;
while ($chip_guess != 0) {
$chip_guess >>= 1;
$chip_size <<= 1;
}
my $mem_round = (int($mem_size / $chip_size) + 1) * $chip_size;
return $mem_round;
}
# determine the individual known information
# NOTICE: forget hw.usermem, it is just (hw.physmem - vm.stats.vm.v_wire_count).
# NOTICE: forget vm.stats.misc.zero_page_count, it is just the subset of
# vm.stats.vm.v_free_count which is already pre-zeroed.
my $mem_hw = &mem_rounded($sysctl->{"hw.physmem"});
my $mem_phys = $sysctl->{"hw.physmem"};
my $mem_all = $sysctl->{"vm.stats.vm.v_page_count"} * $sysctl->{"hw.pagesize"};
my $mem_wire = $sysctl->{"vm.stats.vm.v_wire_count"} * $sysctl->{"hw.pagesize"};
my $mem_active = $sysctl->{"vm.stats.vm.v_active_count"} * $sysctl->{"hw.pagesize"};
my $mem_inactive = $sysctl->{"vm.stats.vm.v_inactive_count"} * $sysctl->{"hw.pagesize"};
my $mem_cache = $sysctl->{"vm.stats.vm.v_cache_count"} * $sysctl->{"hw.pagesize"};
my $mem_free = $sysctl->{"vm.stats.vm.v_free_count"} * $sysctl->{"hw.pagesize"};
# determine the individual unknown information
my $mem_gap_vm = $mem_all - ($mem_wire + $mem_active + $mem_inactive + $mem_cache + $mem_free);
my $mem_gap_sys = $mem_phys - $mem_all;
my $mem_gap_hw = $mem_hw - $mem_phys;
# determine logical summary information
my $mem_used = $mem_wire + $mem_active + $mem_gap_vm;
my $mem_avail = $mem_inactive + $mem_cache + $mem_free;
my $mem_total = $mem_used + $mem_avail;
# information annotations
my $info = {
"mem_wire" => 'Wired: disabled for paging out',
"mem_active" => 'Active: recently referenced',
"mem_inactive" => 'Inactive: recently not referenced',
"mem_cache" => 'Cached: almost avail. for allocation',
"mem_free" => 'Free: fully available for allocation',
"mem_gap_vm" => 'Memory gap: UNKNOWN',
"mem_all" => 'Total real memory managed',
"mem_gap_sys" => 'Memory gap: Kernel?!',
"mem_phys" => 'Total real memory available',
"mem_gap_hw" => 'Memory gap: Segment Mappings?!',
"mem_hw" => 'Total real memory installed',
"mem_used" => 'Logically unused memory',
"mem_avail" => 'Logically available memory',
"mem_total" => 'Logically total memory',
};
# print system results
printf("SYSTEM MEMORY INFORMATION:\n");
printf("mem_wire: %12d (%7dMB) [%3d%%] %s\n", $mem_wire, $mem_wire / (1024*1024), ($mem_wire / $mem_all) * 100, $info->{"mem_wire"});
printf("mem_active: + %12d (%7dMB) [%3d%%] %s\n", $mem_active, $mem_active / (1024*1024), ($mem_active / $mem_all) * 100, $info->{"mem_active"});
printf("mem_inactive:+ %12d (%7dMB) [%3d%%] %s\n", $mem_inactive, $mem_inactive / (1024*1024), ($mem_inactive / $mem_all) * 100, $info->{"mem_inactive"});
printf("mem_cache: + %12d (%7dMB) [%3d%%] %s\n", $mem_cache, $mem_cache / (1024*1024), ($mem_cache / $mem_all) * 100, $info->{"mem_cache"});
printf("mem_free: + %12d (%7dMB) [%3d%%] %s\n", $mem_free, $mem_free / (1024*1024), ($mem_free / $mem_all) * 100, $info->{"mem_free"});
printf("mem_gap_vm: + %12d (%7dMB) [%3d%%] %s\n", $mem_gap_vm, $mem_gap_vm / (1024*1024), ($mem_gap_vm / $mem_all) * 100, $info->{"mem_gap_vm"});
printf("-------------- ------------ ----------- ------\n");
printf("mem_all: = %12d (%7dMB) [100%%] %s\n", $mem_all, $mem_all / (1024*1024), $info->{"mem_all"});
printf("mem_gap_sys: + %12d (%7dMB) %s\n", $mem_gap_sys, $mem_gap_sys / (1024*1024), $info->{"mem_gap_sys"});
printf("-------------- ------------ -----------\n");
printf("mem_phys: = %12d (%7dMB) %s\n", $mem_phys, $mem_phys / (1024*1024), $info->{"mem_phys"});
printf("mem_gap_hw: + %12d (%7dMB) %s\n", $mem_gap_hw, $mem_gap_hw / (1024*1024), $info->{"mem_gap_hw"});
printf("-------------- ------------ -----------\n");
printf("mem_hw: = %12d (%7dMB) %s\n", $mem_hw, $mem_hw / (1024*1024), $info->{"mem_hw"});
# print logical results
printf("\n");
printf("SYSTEM MEMORY SUMMARY:\n");
printf("mem_used: %12d (%7dMB) [%3d%%] %s\n", $mem_used, $mem_used / (1024*1024), ($mem_used / $mem_total) * 100, $info->{"mem_used"});
printf("mem_avail: + %12d (%7dMB) [%3d%%] %s\n", $mem_avail, $mem_avail / (1024*1024), ($mem_avail / $mem_total) * 100, $info->{"mem_avail"});
printf("-------------- ------------ ----------- ------\n");
printf("mem_total: = %12d (%7dMB) [100%%] %s\n", $mem_total, $mem_total / (1024*1024), $info->{"mem_total"});
--a8Wt8u1KmwUX3Y2C--
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