diff options
Diffstat (limited to 'psutil/_pslinux.py')
| -rw-r--r-- | psutil/_pslinux.py | 71 |
1 files changed, 39 insertions, 32 deletions
diff --git a/psutil/_pslinux.py b/psutil/_pslinux.py index 11e62944..1bdeabfe 100644 --- a/psutil/_pslinux.py +++ b/psutil/_pslinux.py @@ -344,34 +344,43 @@ if prlimit is not None: def calculate_avail_vmem(mems): """Fallback for kernels < 3.14 where /proc/meminfo does not provide - "MemAvailable:" column, see: + "MemAvailable", see: https://blog.famzah.net/2014/09/24/ + This code reimplements the algorithm outlined here: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/ commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773 - XXX: on recent kernels this calculation differs by ~1.5% than - "MemAvailable:" as it's calculated slightly differently, see: - https://gitlab.com/procps-ng/procps/issues/42 - https://github.com/famzah/linux-memavailable-procfs/issues/2 + We use this function also when "MemAvailable" returns 0 (possibly a + kernel bug, see: https://github.com/giampaolo/psutil/issues/1915). + In that case this routine matches "free" CLI tool result ("available" + column). + + XXX: on recent kernels this calculation may differ by ~1.5% compared + to "MemAvailable:", as it's calculated slightly differently. It is still way more realistic than doing (free + cached) though. + See: + * https://gitlab.com/procps-ng/procps/issues/42 + * https://github.com/famzah/linux-memavailable-procfs/issues/2 """ - # Fallback for very old distros. According to + # Note about "fallback" value. According to: # https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/ # commit/?id=34e431b0ae398fc54ea69ff85ec700722c9da773 - # ...long ago "avail" was calculated as (free + cached). - # We might fallback in such cases: - # "Active(file)" not available: 2.6.28 / Dec 2008 - # "Inactive(file)" not available: 2.6.28 / Dec 2008 - # "SReclaimable:" not available: 2.6.19 / Nov 2006 - # /proc/zoneinfo not available: 2.6.13 / Aug 2005 + # ...long ago "available" memory was calculated as (free + cached), + # We use fallback when one of these is missing from /proc/meminfo: + # "Active(file)": introduced in 2.6.28 / Dec 2008 + # "Inactive(file)": introduced in 2.6.28 / Dec 2008 + # "SReclaimable": introduced in 2.6.19 / Nov 2006 + # /proc/zoneinfo: introduced in 2.6.13 / Aug 2005 free = mems[b'MemFree:'] fallback = free + mems.get(b"Cached:", 0) try: lru_active_file = mems[b'Active(file):'] lru_inactive_file = mems[b'Inactive(file):'] slab_reclaimable = mems[b'SReclaimable:'] - except KeyError: + except KeyError as err: + debug("%r is missing from /proc/meminfo; using an approximation " + "for calculating available memory" % err.args[0]) return fallback try: f = open_binary('%s/zoneinfo' % get_procfs_path()) @@ -396,19 +405,11 @@ def calculate_avail_vmem(mems): def virtual_memory(): """Report virtual memory stats. - This implementation matches "free" and "vmstat -s" cmdline - utility values and procps-ng-3.3.12 source was used as a reference - (2016-09-18): + This implementation mimicks procps-ng-3.3.12, aka "free" CLI tool: https://gitlab.com/procps-ng/procps/blob/ - 24fd2605c51fccc375ab0287cec33aa767f06718/proc/sysinfo.c - For reference, procps-ng-3.3.10 is the version available on Ubuntu - 16.04. - - Note about "available" memory: up until psutil 4.3 it was - calculated as "avail = (free + buffers + cached)". Now - "MemAvailable:" column (kernel 3.14) from /proc/meminfo is used as - it's more accurate. - That matches "available" column in newer versions of "free". + 24fd2605c51fccc375ab0287cec33aa767f06718/proc/sysinfo.c#L778-791 + The returned values are supposed to match both "free" and "vmstat -s" + CLI tools. """ missing_fields = [] mems = {} @@ -490,17 +491,23 @@ def virtual_memory(): avail = mems[b'MemAvailable:'] except KeyError: avail = calculate_avail_vmem(mems) + else: + if avail == 0: + # Yes, it can happen (probably a kernel bug): + # https://github.com/giampaolo/psutil/issues/1915 + # In this case "free" CLI tool makes an estimate. We do the same, + # and it matches "free" CLI tool. + avail = calculate_avail_vmem(mems) if avail < 0: avail = 0 missing_fields.append('available') - - # If avail is greater than total or our calculation overflows, - # that's symptomatic of running within a LCX container where such - # values will be dramatically distorted over those of the host. - # https://gitlab.com/procps-ng/procps/blob/ - # 24fd2605c51fccc375ab0287cec33aa767f06718/proc/sysinfo.c#L764 - if avail > total: + elif avail > total: + # If avail is greater than total or our calculation overflows, + # that's symptomatic of running within a LCX container where such + # values will be dramatically distorted over those of the host. + # https://gitlab.com/procps-ng/procps/blob/ + # 24fd2605c51fccc375ab0287cec33aa767f06718/proc/sysinfo.c#L764 avail = free percent = usage_percent((total - avail), total, round_=1) |