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library: correct 'used' memory calculations, <meminfo>

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The <meminfo> module attempted to duplicate the former
sysinfo memory calculations wherein 'SReclaimable' was
added to 'Cached' for the 'kb_main_cached' equivalent.

But, this original approach was wrong for two reasons.

1. The addition occurred too late to impact the 'USED'
calculation which could then cause an underflow in the
top memory display if 'SReclaimable' was heavily used.

2. In changing the actual /proc/meminfo 'Cached' value
it meant that users could not rely on that proc(5) man
page when interpreting the MEMINFO_MEM_CACHED results.

So this commit adds a new enumerator for the inclusive
cached amount plus repositions the calculation so that
a MEMINFO_MEM_USED result will exclude 'SReclaimable'.

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2017-05-29 01:11:11 -05:00
committed by Craig Small
parent e3bad0687d
commit dbc880edd3
2 changed files with 10 additions and 4 deletions
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12
proc/meminfo.c
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@ -89,6 +89,7 @@ struct meminfo_data {
unsigned long Writeback;
unsigned long WritebackTmp;
unsigned long derived_mem_cached;
unsigned long derived_mem_hi_used;
unsigned long derived_mem_lo_used;
unsigned long derived_mem_used;
@ -141,6 +142,7 @@ MEM_set(MEM_AVAILABLE, ul_int, MemAvailable)
MEM_set(MEM_BOUNCE, ul_int, Bounce)
MEM_set(MEM_BUFFERS, ul_int, Buffers)
MEM_set(MEM_CACHED, ul_int, Cached)
MEM_set(MEM_CACHED_ALL, ul_int, derived_mem_cached)
MEM_set(MEM_COMMIT_LIMIT, ul_int, CommitLimit)
MEM_set(MEM_COMMITTED_AS, ul_int, Committed_AS)
MEM_set(MEM_HARD_CORRUPTED, ul_int, HardwareCorrupted)
@ -183,6 +185,7 @@ HST_set(DELTA_AVAILABLE, s_int, MemAvailable)
HST_set(DELTA_BOUNCE, s_int, Bounce)
HST_set(DELTA_BUFFERS, s_int, Buffers)
HST_set(DELTA_CACHED, s_int, Cached)
HST_set(DELTA_CACHED_ALL, s_int, derived_mem_cached)
HST_set(DELTA_COMMIT_LIMIT, s_int, CommitLimit)
HST_set(DELTA_COMMITTED_AS, s_int, Committed_AS)
HST_set(DELTA_HARD_CORRUPTED, s_int, HardwareCorrupted)
@ -264,6 +267,7 @@ static struct {
{ RS(MEM_BOUNCE), TS(ul_int) },
{ RS(MEM_BUFFERS), TS(ul_int) },
{ RS(MEM_CACHED), TS(ul_int) },
{ RS(MEM_CACHED_ALL), TS(ul_int) },
{ RS(MEM_COMMIT_LIMIT), TS(ul_int) },
{ RS(MEM_COMMITTED_AS), TS(ul_int) },
{ RS(MEM_HARD_CORRUPTED), TS(ul_int) },
@ -306,6 +310,7 @@ static struct {
{ RS(DELTA_BOUNCE), TS(s_int) },
{ RS(DELTA_BUFFERS), TS(s_int) },
{ RS(DELTA_CACHED), TS(s_int) },
{ RS(DELTA_CACHED_ALL), TS(s_int) },
{ RS(DELTA_COMMIT_LIMIT), TS(s_int) },
{ RS(DELTA_COMMITTED_AS), TS(s_int) },
{ RS(DELTA_HARD_CORRUPTED), TS(s_int) },
@ -617,13 +622,14 @@ static int meminfo_read_failed (
if (0 == mHr(MemAvailable))
mHr(MemAvailable) = mHr(MemFree);
mHr(derived_mem_cached) = mHr(Cached) + mHr(SReclaimable);
/* if 'available' is greater than 'total' or our calculation of mem_used
overflows, that's symptomatic of running within a lxc container where
such values will be dramatically distorted over those of the host. */
if (mHr(MemAvailable) > mHr(MemTotal))
mHr(MemAvailable) = mHr(MemFree);
mem_used = mHr(MemTotal) - mHr(MemFree) - mHr(Cached) - mHr(Buffers);
mem_used = mHr(MemTotal) - mHr(MemFree) - mHr(derived_mem_cached) - mHr(Buffers);
if (mem_used < 0)
mem_used = mHr(MemTotal) - mHr(MemFree);
mHr(derived_mem_used) = (unsigned long)mem_used;
@ -631,8 +637,6 @@ static int meminfo_read_failed (
if (mHr(HighFree) < mHr(HighTotal))
mHr(derived_mem_hi_used) = mHr(HighTotal) - mHr(HighFree);
mHr(Cached) += mHr(SReclaimable);
if (0 == mHr(LowTotal)) {
mHr(LowTotal) = mHr(MemTotal);
mHr(LowFree) = mHr(MemFree);