emo/procps
1
0
Fork 0
Code Issues Pull Requests Packages Releases Activity

library: add support for smaps_rollup file, <pids> api

Browse Source 
A couple of people have suggested that smaps_rollup be
added to the ps program and/or top program. This patch
is intended to set the stage for just such extensions.

There are currently 20 displayable items in the rollup
file. And newlib sometimes uses sscanf when populating
the target, sometimes hsearch and one customized gperf
approach. None of these fit well with the smaps items.

Thus, an approach using a simple table lookup was used
and, by disabling 1 code line, it could be made immune
from changes to the items order (unlike a sscanf call)
and doesn't carry the greater cost of a hsearch/gperf.

Note: The next patch will allow top to display some of
these new fields. Then, it'll be possible to determine
the colossal costs of accessing the smaps_rollup file.

Here is a small preview of just what you will discover
when using the command 'time top/top -d0 -n1000' while
configured with just two fields: PID + 1 memory field.

------------------------------------ as a regular user
    with only PID + RES (statm)
real       0m2.605s
user       0m1.060s
sys        0m1.377s
    with only PID + RSS (smaps)
real      0m26.397s                    10x more costly
user       0m1.253s
sys       0m24.915s

----------------- as a root (thus smaps for all tasks)
    with only PID + RES (statm)
real       0m2.651s
user       0m1.177s
sys        0m1.286s
    with only PID + RSS (smaps)
real      0m33.040s                    12x more costly
user       0m1.256s
sys       0m31.533s

Reference(s):
. ps: expose shared/private memory separately
https://gitlab.com/procps-ng/procps/-/issues/201
. top/ps: add support for PSS reporting
https://gitlab.com/procps-ng/procps/-/issues/112

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2021-04-26 00:00:00 -05:00
committed by Craig Small
parent b921776dad
commit 12543b6c76
4 changed files with 165 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

77
proc/readproc.c
View File

@@ -648,6 +648,72 @@ static void io2proc(const char* s, proc_t *restrict P) {
&P->syscw, &P->read_bytes, &P->write_bytes, &P->cancelled_write_bytes);
}
// Assuming permissions have allowed the read of smaps_rollup, this
// guy will extract some %lu data. Considering the number of items,
// we are between small enough to use a sscanf and large enough for
// a search.h approach. Thus we roll (get it?) our own custom code.
static void smaps2proc (const char* s, proc_t *restrict P) {
#define enMAX (int)((sizeof(smaptab) / sizeof(smaptab[0])))
// 1st proc_t data field
#define fZERO tid
// a smaptab entry generator
#define mkENT(F) { #F ":", -1, (int)((void*)&q->smap_ ## F - (void*)&q->fZERO) }
// make a target field
#define mkOBJ(e) ( (unsigned long *)((void *)&P->fZERO + smaptab[e].offs) )
static const proc_t *q;
static struct {
const char *item;
int slen;
int offs;
} smaptab[] = {
/* Size smaps only, not rollup */
/* KernelPageSize " */
/* MMUPageSize " */
mkENT(Rss),
mkENT(Pss),
mkENT(Pss_Anon), /* rollup only, not smaps */
mkENT(Pss_File), /* " */
mkENT(Pss_Shmem), /* " */
mkENT(Shared_Clean),
mkENT(Shared_Dirty),
mkENT(Private_Clean),
mkENT(Private_Dirty),
mkENT(Referenced),
mkENT(Anonymous),
mkENT(LazyFree),
mkENT(AnonHugePages),
mkENT(ShmemPmdMapped),
mkENT(FilePmdMapped),
mkENT(Shared_Hugetlb),
mkENT(Private_Hugetlb),
mkENT(Swap),
mkENT(SwapPss),
mkENT(Locked)
/* THPeligible smaps only, not rollup */
/* ProtectionKey " */
/* VmFlags " */
};
char *head, *tail;
int i;
if (smaptab[0].slen < 0) {
for (i = 0; i < enMAX; i++)
smaptab[i].slen = (int)strlen(smaptab[i].item);
}
for (i = 0; i < enMAX; i++) {
if (!(head = strstr(s, smaptab[i].item)))
continue;
head += smaptab[i].slen;
*mkOBJ(i) = strtoul(head, &tail, 10);
// saves some overhead BUT makes us dependent on current order
s = tail;
}
#undef enMAX
#undef fZERO
#undef mkENT
#undef mkOBJ
}
static int file2str(const char *directory, const char *what, struct utlbuf_s *ub) {
#define buffGRW 1024
char path[PROCPATHLEN];
@@ -1054,6 +1120,11 @@ static proc_t* simple_readproc(PROCTAB *restrict const PT, proc_t *restrict cons
io2proc(ub.buf, p);
}
if (flags & PROC_FILLSMAPS) { // read /proc/#/smaps_rollup
if (file2str(path, "smaps_rollup", &ub) != -1)
smaps2proc(ub.buf, p);
}
if (flags & PROC_FILLMEM) { // read /proc/#/statm
if (file2str(path, "statm", &ub) != -1)
statm2proc(ub.buf, p);
@@ -1169,10 +1240,16 @@ static proc_t* simple_readtask(PROCTAB *restrict const PT, proc_t *restrict cons
io2proc(ub.buf, t);
}
if (flags & PROC_FILLSMAPS) { // read /proc/#/task/#/smaps_rollup
if (file2str(path, "smaps_rollup", &ub) != -1)
smaps2proc(ub.buf, t);
}
if (flags & PROC_FILLMEM) { // read /proc/#/task/#/statm
if (file2str(path, "statm", &ub) != -1)
statm2proc(ub.buf, t);
}
if (flags & PROC_FILLSTATUS) { // read /proc/#/task/#/status
if (file2str(path, "status", &ub) != -1) {
rc += status2proc(ub.buf, t, 0);