Revision 15f9850d3c2d46f5851a424d2990a18b5bb5ebfd authored by David S. Miller on 19 May 2005, 05:49:26 UTC, committed by David S. Miller on 19 May 2005, 05:49:26 UTC
Even though we do software interrupt mitigation via NAPI, it still helps to have some minimal hw assisted mitigation. This helps, particularly, on systems where register I/O overhead is much greater than the CPU horsepower. For example, it helps on NUMA systems. In such cases the PIO overhead to disable interrupts for NAPI accounts for the majority of the packet processing cost. The CPU is fast enough such that only a single packet is processed by each NAPI poll call. Thanks to Michael Chan for reviewing this patch. Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent fac9b83
acct.c
/*
* linux/kernel/acct.c
*
* BSD Process Accounting for Linux
*
* Author: Marco van Wieringen <mvw@planets.elm.net>
*
* Some code based on ideas and code from:
* Thomas K. Dyas <tdyas@eden.rutgers.edu>
*
* This file implements BSD-style process accounting. Whenever any
* process exits, an accounting record of type "struct acct" is
* written to the file specified with the acct() system call. It is
* up to user-level programs to do useful things with the accounting
* log. The kernel just provides the raw accounting information.
*
* (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
*
* Plugged two leaks. 1) It didn't return acct_file into the free_filps if
* the file happened to be read-only. 2) If the accounting was suspended
* due to the lack of space it happily allowed to reopen it and completely
* lost the old acct_file. 3/10/98, Al Viro.
*
* Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
* XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
*
* Fixed a nasty interaction with with sys_umount(). If the accointing
* was suspeneded we failed to stop it on umount(). Messy.
* Another one: remount to readonly didn't stop accounting.
* Question: what should we do if we have CAP_SYS_ADMIN but not
* CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
* unless we are messing with the root. In that case we are getting a
* real mess with do_remount_sb(). 9/11/98, AV.
*
* Fixed a bunch of races (and pair of leaks). Probably not the best way,
* but this one obviously doesn't introduce deadlocks. Later. BTW, found
* one race (and leak) in BSD implementation.
* OK, that's better. ANOTHER race and leak in BSD variant. There always
* is one more bug... 10/11/98, AV.
*
* Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
* ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
* a struct file opened for write. Fixed. 2/6/2000, AV.
*/
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/acct.h>
#include <linux/file.h>
#include <linux/tty.h>
#include <linux/security.h>
#include <linux/vfs.h>
#include <linux/jiffies.h>
#include <linux/times.h>
#include <linux/syscalls.h>
#include <asm/uaccess.h>
#include <asm/div64.h>
#include <linux/blkdev.h> /* sector_div */
/*
* These constants control the amount of freespace that suspend and
* resume the process accounting system, and the time delay between
* each check.
* Turned into sysctl-controllable parameters. AV, 12/11/98
*/
int acct_parm[3] = {4, 2, 30};
#define RESUME (acct_parm[0]) /* >foo% free space - resume */
#define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
#define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
/*
* External references and all of the globals.
*/
static void do_acct_process(long, struct file *);
/*
* This structure is used so that all the data protected by lock
* can be placed in the same cache line as the lock. This primes
* the cache line to have the data after getting the lock.
*/
struct acct_glbs {
spinlock_t lock;
volatile int active;
volatile int needcheck;
struct file *file;
struct timer_list timer;
};
static struct acct_glbs acct_globals __cacheline_aligned = {SPIN_LOCK_UNLOCKED};
/*
* Called whenever the timer says to check the free space.
*/
static void acct_timeout(unsigned long unused)
{
acct_globals.needcheck = 1;
}
/*
* Check the amount of free space and suspend/resume accordingly.
*/
static int check_free_space(struct file *file)
{
struct kstatfs sbuf;
int res;
int act;
sector_t resume;
sector_t suspend;
spin_lock(&acct_globals.lock);
res = acct_globals.active;
if (!file || !acct_globals.needcheck)
goto out;
spin_unlock(&acct_globals.lock);
/* May block */
if (vfs_statfs(file->f_dentry->d_inode->i_sb, &sbuf))
return res;
suspend = sbuf.f_blocks * SUSPEND;
resume = sbuf.f_blocks * RESUME;
sector_div(suspend, 100);
sector_div(resume, 100);
if (sbuf.f_bavail <= suspend)
act = -1;
else if (sbuf.f_bavail >= resume)
act = 1;
else
act = 0;
/*
* If some joker switched acct_globals.file under us we'ld better be
* silent and _not_ touch anything.
*/
spin_lock(&acct_globals.lock);
if (file != acct_globals.file) {
if (act)
res = act>0;
goto out;
}
if (acct_globals.active) {
if (act < 0) {
acct_globals.active = 0;
printk(KERN_INFO "Process accounting paused\n");
}
} else {
if (act > 0) {
acct_globals.active = 1;
printk(KERN_INFO "Process accounting resumed\n");
}
}
del_timer(&acct_globals.timer);
acct_globals.needcheck = 0;
acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
add_timer(&acct_globals.timer);
res = acct_globals.active;
out:
spin_unlock(&acct_globals.lock);
return res;
}
/*
* Close the old accouting file (if currently open) and then replace
* it with file (if non-NULL).
*
* NOTE: acct_globals.lock MUST be held on entry and exit.
*/
static void acct_file_reopen(struct file *file)
{
struct file *old_acct = NULL;
if (acct_globals.file) {
old_acct = acct_globals.file;
del_timer(&acct_globals.timer);
acct_globals.active = 0;
acct_globals.needcheck = 0;
acct_globals.file = NULL;
}
if (file) {
acct_globals.file = file;
acct_globals.needcheck = 0;
acct_globals.active = 1;
/* It's been deleted if it was used before so this is safe */
init_timer(&acct_globals.timer);
acct_globals.timer.function = acct_timeout;
acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
add_timer(&acct_globals.timer);
}
if (old_acct) {
spin_unlock(&acct_globals.lock);
do_acct_process(0, old_acct);
filp_close(old_acct, NULL);
spin_lock(&acct_globals.lock);
}
}
/*
* sys_acct() is the only system call needed to implement process
* accounting. It takes the name of the file where accounting records
* should be written. If the filename is NULL, accounting will be
* shutdown.
*/
asmlinkage long sys_acct(const char __user *name)
{
struct file *file = NULL;
char *tmp;
int error;
if (!capable(CAP_SYS_PACCT))
return -EPERM;
if (name) {
tmp = getname(name);
if (IS_ERR(tmp)) {
return (PTR_ERR(tmp));
}
/* Difference from BSD - they don't do O_APPEND */
file = filp_open(tmp, O_WRONLY|O_APPEND, 0);
putname(tmp);
if (IS_ERR(file)) {
return (PTR_ERR(file));
}
if (!S_ISREG(file->f_dentry->d_inode->i_mode)) {
filp_close(file, NULL);
return (-EACCES);
}
if (!file->f_op->write) {
filp_close(file, NULL);
return (-EIO);
}
}
error = security_acct(file);
if (error) {
if (file)
filp_close(file, NULL);
return error;
}
spin_lock(&acct_globals.lock);
acct_file_reopen(file);
spin_unlock(&acct_globals.lock);
return (0);
}
/*
* If the accouting is turned on for a file in the filesystem pointed
* to by sb, turn accouting off.
*/
void acct_auto_close(struct super_block *sb)
{
spin_lock(&acct_globals.lock);
if (acct_globals.file &&
acct_globals.file->f_dentry->d_inode->i_sb == sb) {
acct_file_reopen((struct file *)NULL);
}
spin_unlock(&acct_globals.lock);
}
/*
* encode an unsigned long into a comp_t
*
* This routine has been adopted from the encode_comp_t() function in
* the kern_acct.c file of the FreeBSD operating system. The encoding
* is a 13-bit fraction with a 3-bit (base 8) exponent.
*/
#define MANTSIZE 13 /* 13 bit mantissa. */
#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
static comp_t encode_comp_t(unsigned long value)
{
int exp, rnd;
exp = rnd = 0;
while (value > MAXFRACT) {
rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
exp++;
}
/*
* If we need to round up, do it (and handle overflow correctly).
*/
if (rnd && (++value > MAXFRACT)) {
value >>= EXPSIZE;
exp++;
}
/*
* Clean it up and polish it off.
*/
exp <<= MANTSIZE; /* Shift the exponent into place */
exp += value; /* and add on the mantissa. */
return exp;
}
#if ACCT_VERSION==1 || ACCT_VERSION==2
/*
* encode an u64 into a comp2_t (24 bits)
*
* Format: 5 bit base 2 exponent, 20 bits mantissa.
* The leading bit of the mantissa is not stored, but implied for
* non-zero exponents.
* Largest encodable value is 50 bits.
*/
#define MANTSIZE2 20 /* 20 bit mantissa. */
#define EXPSIZE2 5 /* 5 bit base 2 exponent. */
#define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
#define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
static comp2_t encode_comp2_t(u64 value)
{
int exp, rnd;
exp = (value > (MAXFRACT2>>1));
rnd = 0;
while (value > MAXFRACT2) {
rnd = value & 1;
value >>= 1;
exp++;
}
/*
* If we need to round up, do it (and handle overflow correctly).
*/
if (rnd && (++value > MAXFRACT2)) {
value >>= 1;
exp++;
}
if (exp > MAXEXP2) {
/* Overflow. Return largest representable number instead. */
return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
} else {
return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
}
}
#endif
#if ACCT_VERSION==3
/*
* encode an u64 into a 32 bit IEEE float
*/
static u32 encode_float(u64 value)
{
unsigned exp = 190;
unsigned u;
if (value==0) return 0;
while ((s64)value > 0){
value <<= 1;
exp--;
}
u = (u32)(value >> 40) & 0x7fffffu;
return u | (exp << 23);
}
#endif
/*
* Write an accounting entry for an exiting process
*
* The acct_process() call is the workhorse of the process
* accounting system. The struct acct is built here and then written
* into the accounting file. This function should only be called from
* do_exit().
*/
/*
* do_acct_process does all actual work. Caller holds the reference to file.
*/
static void do_acct_process(long exitcode, struct file *file)
{
acct_t ac;
mm_segment_t fs;
unsigned long vsize;
unsigned long flim;
u64 elapsed;
u64 run_time;
struct timespec uptime;
/*
* First check to see if there is enough free_space to continue
* the process accounting system.
*/
if (!check_free_space(file))
return;
/*
* Fill the accounting struct with the needed info as recorded
* by the different kernel functions.
*/
memset((caddr_t)&ac, 0, sizeof(acct_t));
ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
/* calculate run_time in nsec*/
do_posix_clock_monotonic_gettime(&uptime);
run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
run_time -= (u64)current->start_time.tv_sec*NSEC_PER_SEC
+ current->start_time.tv_nsec;
/* convert nsec -> AHZ */
elapsed = nsec_to_AHZ(run_time);
#if ACCT_VERSION==3
ac.ac_etime = encode_float(elapsed);
#else
ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
(unsigned long) elapsed : (unsigned long) -1l);
#endif
#if ACCT_VERSION==1 || ACCT_VERSION==2
{
/* new enlarged etime field */
comp2_t etime = encode_comp2_t(elapsed);
ac.ac_etime_hi = etime >> 16;
ac.ac_etime_lo = (u16) etime;
}
#endif
do_div(elapsed, AHZ);
ac.ac_btime = xtime.tv_sec - elapsed;
ac.ac_utime = encode_comp_t(jiffies_to_AHZ(
current->signal->utime +
current->group_leader->utime));
ac.ac_stime = encode_comp_t(jiffies_to_AHZ(
current->signal->stime +
current->group_leader->stime));
/* we really need to bite the bullet and change layout */
ac.ac_uid = current->uid;
ac.ac_gid = current->gid;
#if ACCT_VERSION==2
ac.ac_ahz = AHZ;
#endif
#if ACCT_VERSION==1 || ACCT_VERSION==2
/* backward-compatible 16 bit fields */
ac.ac_uid16 = current->uid;
ac.ac_gid16 = current->gid;
#endif
#if ACCT_VERSION==3
ac.ac_pid = current->tgid;
ac.ac_ppid = current->parent->tgid;
#endif
read_lock(&tasklist_lock); /* pin current->signal */
ac.ac_tty = current->signal->tty ?
old_encode_dev(tty_devnum(current->signal->tty)) : 0;
read_unlock(&tasklist_lock);
ac.ac_flag = 0;
if (current->flags & PF_FORKNOEXEC)
ac.ac_flag |= AFORK;
if (current->flags & PF_SUPERPRIV)
ac.ac_flag |= ASU;
if (current->flags & PF_DUMPCORE)
ac.ac_flag |= ACORE;
if (current->flags & PF_SIGNALED)
ac.ac_flag |= AXSIG;
vsize = 0;
if (current->mm) {
struct vm_area_struct *vma;
down_read(¤t->mm->mmap_sem);
vma = current->mm->mmap;
while (vma) {
vsize += vma->vm_end - vma->vm_start;
vma = vma->vm_next;
}
up_read(¤t->mm->mmap_sem);
}
vsize = vsize / 1024;
ac.ac_mem = encode_comp_t(vsize);
ac.ac_io = encode_comp_t(0 /* current->io_usage */); /* %% */
ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
ac.ac_minflt = encode_comp_t(current->signal->min_flt +
current->group_leader->min_flt);
ac.ac_majflt = encode_comp_t(current->signal->maj_flt +
current->group_leader->maj_flt);
ac.ac_swaps = encode_comp_t(0);
ac.ac_exitcode = exitcode;
/*
* Kernel segment override to datasegment and write it
* to the accounting file.
*/
fs = get_fs();
set_fs(KERNEL_DS);
/*
* Accounting records are not subject to resource limits.
*/
flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
file->f_op->write(file, (char *)&ac,
sizeof(acct_t), &file->f_pos);
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
set_fs(fs);
}
/*
* acct_process - now just a wrapper around do_acct_process
*/
void acct_process(long exitcode)
{
struct file *file = NULL;
/*
* accelerate the common fastpath:
*/
if (!acct_globals.file)
return;
spin_lock(&acct_globals.lock);
file = acct_globals.file;
if (unlikely(!file)) {
spin_unlock(&acct_globals.lock);
return;
}
get_file(file);
spin_unlock(&acct_globals.lock);
do_acct_process(exitcode, file);
fput(file);
}
/*
* acct_update_integrals
* - update mm integral fields in task_struct
*/
void acct_update_integrals(struct task_struct *tsk)
{
if (likely(tsk->mm)) {
long delta = tsk->stime - tsk->acct_stimexpd;
if (delta == 0)
return;
tsk->acct_stimexpd = tsk->stime;
tsk->acct_rss_mem1 += delta * get_mm_counter(tsk->mm, rss);
tsk->acct_vm_mem1 += delta * tsk->mm->total_vm;
}
}
/*
* acct_clear_integrals
* - clear the mm integral fields in task_struct
*/
void acct_clear_integrals(struct task_struct *tsk)
{
if (tsk) {
tsk->acct_stimexpd = 0;
tsk->acct_rss_mem1 = 0;
tsk->acct_vm_mem1 = 0;
}
}
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