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photoproc: chdir() reduces overhead syscalls and kernel context switches #370

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photoproc: chdir() reduces overhead syscalls and kernel context switches #370

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133 changes: 57 additions & 76 deletions photoproc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -59,13 +59,13 @@
"%*d %*d %*d %*d %*d %*d " \
"%d %d %d %lld"

static int procstat(struct tstat *, unsigned long long, char);
static int procstatus(struct tstat *);
static int procio(struct tstat *);
static void proccmd(struct tstat *);
static void procsmaps(struct tstat *);
static void procwchan(struct tstat *);
static count_t procschedstat(struct tstat *);
static int procstat(struct tstat *, unsigned long long, char, char*);
static int procstatus(struct tstat *, char*);
static int procio(struct tstat *, char*);
static void proccmd(struct tstat *, char*);
static void procsmaps(struct tstat *, char*);
static void procwchan(struct tstat *, char*);
static count_t procschedstat(struct tstat *, char*);

extern GHashTable *ghash_net;

Expand Down Expand Up @@ -165,40 +165,28 @@ photoproc(struct tstat *tasklist, int maxtask)
if (!isdigit(entp->d_name[0]))
continue;

/*
** change to the process' subdirectory
*/
if ( chdir(entp->d_name) != 0 )
continue;

/*
** gather process-level information
*/
curtask = tasklist+tval;

if ( !procstat(curtask, bootepoch, 1)) /* from /proc/pid/stat */
if ( !procstat(curtask, bootepoch, 1, entp->d_name)) /* from /proc/pid/stat */
{
if ( chdir("..") == -1)
;
continue;
}

if ( !procstatus(curtask) ) /* from /proc/pid/status */
if ( !procstatus(curtask, entp->d_name) ) /* from /proc/pid/status */
{
if ( chdir("..") == -1)
;
continue;
}

if ( !procio(curtask) ) /* from /proc/pid/io */
if ( !procio(curtask, entp->d_name) ) /* from /proc/pid/io */
{
if ( chdir("..") == -1)
;
continue;
}

procschedstat(curtask); /* from /proc/pid/schedstat */
proccmd(curtask); /* from /proc/pid/cmdline */
procschedstat(curtask, entp->d_name); /* from /proc/pid/schedstat */
proccmd(curtask, entp->d_name); /* from /proc/pid/cmdline */
dockstat += getutsname(curtask); /* retrieve container/pod name */

/*
Expand All @@ -207,14 +195,14 @@ photoproc(struct tstat *tasklist, int maxtask)
** so gathering this info is optional
*/
if (calcpss)
procsmaps(curtask); /* from /proc/pid/smaps */
procsmaps(curtask, entp->d_name); /* from /proc/pid/smaps */

/*
** determine thread's wchan, if wanted ('expensive' from
** a CPU consumption point-of-view)
*/
if (getwchan)
procwchan(curtask);
procwchan(curtask, entp->d_name);

if (supportflags & NETATOPBPF) {
struct taskcount *tc = g_hash_table_lookup(ghash_net, &(curtask->gen.tgid));
Expand Down Expand Up @@ -245,6 +233,7 @@ photoproc(struct tstat *tasklist, int maxtask)
{
DIR *dirtask;
struct dirent *tent;
char taskdir[4096];

curtask->gen.nthrrun = 0;
curtask->gen.nthrslpi = 0;
Expand All @@ -270,53 +259,36 @@ photoproc(struct tstat *tasklist, int maxtask)
/*
** open underlying task directory
*/
if ( chdir("task") == 0 )
sprintf(taskdir, "%s/task", entp->d_name);
if ( (dirtask = opendir(taskdir)) != NULL )
{
unsigned long cur_nth = 0;

dirtask = opendir(".");

/*
** due to race condition, opendir() might
** have failed (leave task and process-level
** directories)
*/
if( dirtask == NULL )
{
if(chdir("../..") == -1)
;
continue;
}
char threaddir[4096];

while ((tent=readdir(dirtask)) && tval<maxtask)
{
struct tstat *curthr = tasklist+tval;

/*
** change to the thread's subdirectory
** skip non-numerical names
*/
if ( tent->d_name[0] == '.' ||
chdir(tent->d_name) != 0 )
if ( !isdigit(tent->d_name[0]) )
continue;

if ( !procstat(curthr, bootepoch, 0))
sprintf(threaddir, "%s/%s", taskdir, tent->d_name);

if ( !procstat(curthr, bootepoch, 0, threaddir))
{
if ( chdir("..") == -1)
;
continue;
}

if ( !procstatus(curthr) )
if ( !procstatus(curthr, threaddir) )
{
if ( chdir("..") == -1)
;
continue;
}

if ( !procio(curthr) )
if ( !procio(curthr, threaddir) )
{
if ( chdir("..") == -1)
;
continue;
}

Expand All @@ -326,11 +298,11 @@ photoproc(struct tstat *tasklist, int maxtask)
** point-of-view)
*/
if (getwchan)
procwchan(curthr);
procwchan(curthr, threaddir);

// totalize values of all threads
curtask->cpu.rundelay +=
procschedstat(curthr);
procschedstat(curthr, threaddir);

curtask->cpu.blkdelay +=
curthr->cpu.blkdelay;
Expand Down Expand Up @@ -372,21 +344,15 @@ photoproc(struct tstat *tasklist, int maxtask)
tval++; /* increment thread-level */
cur_nth++; /* increment # threads */

if ( chdir("..") == -1)
; /* thread */
}

closedir(dirtask);
if ( chdir("..") == -1)
; /* leave task */

// calibrate number of threads
curtask->gen.nthr = cur_nth;
}
}

if ( chdir("..") == -1)
; /* leave process-level directry */
}

closedir(dirp);
Expand Down Expand Up @@ -494,13 +460,15 @@ counttasks(void)
** open file "stat" and obtain required info
*/
static int
procstat(struct tstat *curtask, unsigned long long bootepoch, char isproc)
procstat(struct tstat *curtask, unsigned long long bootepoch, char isproc, char *path)
{
FILE *fp;
int nr;
char line[4096], *p, *cmdhead, *cmdtail;
char filepath[4096];

if ( (fp = fopen("stat", "r")) == NULL)
sprintf(filepath, "%s/stat", path);
if ( (fp = fopen(filepath, "r")) == NULL)
return 0;

if ( (nr = fread(line, 1, sizeof line-1, fp)) == 0)
Expand Down Expand Up @@ -596,12 +564,14 @@ procstat(struct tstat *curtask, unsigned long long bootepoch, char isproc)
** open file "status" and obtain required info
*/
static int
procstatus(struct tstat *curtask)
procstatus(struct tstat *curtask, char *path)
{
FILE *fp;
char line[4096];
char filepath[4096];

if ( (fp = fopen("status", "r")) == NULL)
sprintf(filepath, "%s/status", path);
if ( (fp = fopen(filepath, "r")) == NULL)
return 0;

curtask->gen.nthr = 1; /* for compat with 2.4 */
Expand Down Expand Up @@ -724,17 +694,19 @@ procstatus(struct tstat *curtask)
#define IO_WRITE "write_bytes:"
#define IO_CWRITE "cancelled_write_bytes:"
static int
procio(struct tstat *curtask)
procio(struct tstat *curtask, char *path)
{
FILE *fp;
char line[4096];
count_t dskrsz=0, dskwsz=0, dskcwsz=0;
char filepath[4096];

if (supportflags & IOSTAT)
{
regainrootprivs();

if ( (fp = fopen("io", "r")) )
sprintf(filepath, "%s/io", path);
if ( (fp = fopen(filepath, "r")) )
{
while (fgets(line, sizeof line, fp))
{
Expand Down Expand Up @@ -794,18 +766,20 @@ procio(struct tstat *curtask)
#define ABBENVLEN 16

static void
proccmd(struct tstat *curtask)
proccmd(struct tstat *curtask, char *path)
{
FILE *fp, *fpe;
register int i, nr;
ssize_t env_len = 0;
register char *pc = curtask->gen.cmdline;
char filepath[4096];

memset(curtask->gen.cmdline, 0, CMDLEN+1); // initialize command line

// prepend by environment variables (if required)
//
if ( prependenv && (fpe = fopen("environ", "r")) != NULL)
sprintf(filepath, "%s/environ", path);
if ( prependenv && (fpe = fopen(filepath, "r")) != NULL)
{
char *line = NULL;
ssize_t nread;
Expand Down Expand Up @@ -851,7 +825,8 @@ proccmd(struct tstat *curtask)

// add command line and parameters
//
if ( (fp = fopen("cmdline", "r")) != NULL)
sprintf(filepath, "%s/cmdline", path);
if ( (fp = fopen(filepath, "r")) != NULL)
{
nr = fread(pc, 1, CMDLEN-env_len, fp);
fclose(fp);
Expand Down Expand Up @@ -888,12 +863,14 @@ proccmd(struct tstat *curtask)
** has been put in sleep state)
*/
static void
procwchan(struct tstat *curtask)
procwchan(struct tstat *curtask, char *path)
{
FILE *fp;
register int nr = 0;
char filepath[4096];

if ( (fp = fopen("wchan", "r")) != NULL)
sprintf(filepath, "%s/wchan", path);
if ( (fp = fopen(filepath, "r")) != NULL)
{

nr = fread(curtask->cpu.wchan, 1,
Expand All @@ -914,13 +891,14 @@ procwchan(struct tstat *curtask)
** if kernel supports "smaps_rollup", use "smaps_rollup" instead
*/
static void
procsmaps(struct tstat *curtask)
procsmaps(struct tstat *curtask, char *path)
{
FILE *fp;
char line[4096];
count_t pssval;
static int procsmaps_firstcall = 1;
static char *smapsfile = "smaps";
char filepath[4096];

if (procsmaps_firstcall)
{
Expand All @@ -939,7 +917,8 @@ procsmaps(struct tstat *curtask)
*/
regainrootprivs();

if ( (fp = fopen(smapsfile, "r")) )
sprintf(filepath, "%s/%s", path, smapsfile);
if ( (fp = fopen(filepath, "r")) )
{
curtask->mem.pmem = 0;

Expand Down Expand Up @@ -975,18 +954,20 @@ procsmaps(struct tstat *curtask)
** ref: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/scheduler/sched-stats.rst?h=v5.7-rc6
*/
static count_t
procschedstat(struct tstat *curtask)
procschedstat(struct tstat *curtask, char *path)
{
FILE *fp;
char line[4096];
count_t runtime, rundelay = 0;
unsigned long pcount;
static char *schedstatfile = "schedstat";
char filepath[4096];

/*
** open the schedstat file
*/
if ( (fp = fopen(schedstatfile, "r")) )
sprintf(filepath, "%s/%s", path, schedstatfile);
if ( (fp = fopen(filepath, "r")) )
{
curtask->cpu.rundelay = 0;

Expand Down