1修改進(jìn)程資源限制，軟限制可改，最大值不能超過硬限制，硬限制只有root用戶可以修改

查看進(jìn)程資源限制

cat /proc/self/limits

ulimit -a?????????????????????????????????

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2getrlimit()函數(shù)和setrlimit()函數(shù)

A依賴的頭文件

#include<sys/time.h>

#include<sys/resource.h>

B函數(shù)聲明

int getrlimit(int resource, struct rlimit*rlim);

int setrlimit(int resource, const structrlimit *rlim);

int prlimit(pid_t pid, int resource, conststruct rlimit *new_limit,

??????????????????struct rlimit *old_limit);

函數(shù)說明：通過getrlimit,setrlimit,prlimit函數(shù)來獲得或者設(shè)置資源的limits

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描述信息

The?getrlimit() and setrlimit() system calls get and set resource limitsrespectively.?Each resource has anassociated soft and hard limit,as defined by the rlimit structure:

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??????????struct rlimit {

??????????????rlim_t rlim_cur;? /* Soft limit */

??????????????rlim_t rlim_max;? /* Hard limit (ceiling for rlim_cur) */

??????????};

翻譯：這個getrlimit()和setrlimit()函數(shù)分別獲得和設(shè)置資源的limits,每個資源有一個關(guān)聯(lián)的軟限制和硬限制，它們被定義在rlimit結(jié)構(gòu)體中。

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The?soft?limit? is? thevalue that the kernel enforces for the corre‐

??????sponding resource.?The hard limitacts? as?a?ceiling? for?the?soft

??????limit:?an? unprivileged process may set only its softlimit to a value

??????in the range from 0 up to the hard limit, and (irreversibly) lower?its

??????hard??limit.??? A?privileged?process? (under?Linux:?one? with?the

??????CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit

??????value.

The resource argument must be one of:

RLIMIT_AS

?????????????The maximum size of the process'svirtual memory (address space)

?????????????in bytes.? This limit?affects?calls? to?brk(2),?mmap(2)? and

?????????????mremap(2),? which fail with the error ENOMEM uponexceeding this

?????????????limit.? Also automatic stack expansion will fail (andgenerate a

?????????????SIGSEGV? that?kills?the process if no alternatestack has been

?????????????made available viasigaltstack(2)).? Since the value isa?long,

?????????????on? machines?with?a 32-bit long either thislimit is at most 2

?????????????GiB, or this resource isunlimited.

RLIMIT_CORE

?????????????Maximum size of core file.? When 0 no core dump files?are?cre‐

?????????????ated.? When nonzero, larger dumps are truncated tothis size.
RLIMIT_CPU

?????????????CPU?time?limit? in seconds.?When the process reaches the soft

?????????????limit, it is sent a SIGXCPUsignal.? The default action for this

?????????????signal? is to terminate the process.?However, the signal can be

?????????????caught, and the handler canreturn control to the main? program.

?????????????If? the?process?continues to consume CPUtime, it will be sent

?????????????SIGXCPU once per second untilthe? hard?limit?is? reached,?at

?????????????which? time?it?is? sent SIGKILL.?(This latter point describes

?????????????Linux behavior.? Implementations vary in?how?they? treat?pro‐

?????????????cesses? which?continue?to? consume CPU time after reaching the

?????????????soft limit.? Portable applications that need to catchthis?sig‐

?????????????nal? should perform an orderly termination uponfirst receipt of

?????????????SIGXCPU.)

RLIMIT_DATA

?????????????The maximum size of? the?process's?data? segment?(initialized

?????????????data,? uninitialized?data, and heap).?This limitaffects calls

?????????????to brk(2) and sbrk(2), which failwith? the?error?ENOMEM? upon

?????????????encountering the soft limit ofthis resource.

RLIMIT_FSIZE

?????????????The maximum size of files that theprocess may create.? Attempts

?????????????to extend a file beyond this? limit?result?in? delivery?of?a

?????????????SIGXFSZ? signal.??By default, this signal terminates a process,

?????????????but a process can catch thissignal instead, in which? case? the

?????????????relevant? system?call?(e.g., write(2),truncate(2)) fails with

?????????????the error EFBIG.

RLIMIT_LOCKS (Early Linux 2.4 only)

?????????????A limit on the combined number offlock(2)? locks?and?fcntl(2)

?????????????leases that this process mayestablish.

RLIMIT_MEMLOCK

?????????????The? maximum?number?of bytes of memory thatmay be locked into

?????????????RAM.? In effect this limit is rounded down to thenearest multi‐

?????????????ple? of?the? system page size.? This limit affects mlock(2) and

?????????????mlockall(2) and the mmap(2)MAP_LOCKED operation.?? Since?Linux

?????????????2.6.9 it also affects theshmctl(2) SHM_LOCK operation, where it

?????????????sets a maximum on the total bytesin shared memory segments (see

?????????????shmget(2)) that may be locked bythe real user ID of the calling

?????????????process.? The shmctl(2) SHM_LOCK locks areaccounted?for? sepa‐

?????????????rately?? from??the?per-process? memory?locks?established? by

?????????????mlock(2), mlockall(2), andmmap(2)? MAP_LOCKED;?a?process? can

?????????????lock bytes up to this limit ineach of these two categories.?In

?????????????Linux kernels before 2.6.9, thislimit controlled the amount?of

?????????????memory? that?could?be? locked?by a privileged process.?Since

?????????????Linux 2.6.9, no limits are placedon the amount of memory that a

?????????????privileged? process may lock, and this limit insteadgoverns the

?????????????amount of memory that anunprivileged process may lock.

RLIMIT_MSGQUEUE (Since Linux 2.6.8)

?????????????Specifies the limit on the numberof bytes that can be allocated

?????????????for? POSIX?message?queues? for the real user ID of the calling

?????????????process.? This limit is enforced for mq_open(3).??Each?message

?????????????queue that the user createscounts (until it is removed) against

?????????????this limit according to theformula:

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?????????????????bytes = attr.mq_maxmsg *sizeof(struct msg_msg *) +

?????????????????????????attr.mq_maxmsg *attr.mq_msgsize

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?????????????where attr is the mq_attr? structure?specified?as? the?fourth

?????????????argument to mq_open(3).

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?????????????The? first?addend?in the formula, whichincludes sizeof(struct

?????????????msg_msg *) (4 bytes onLinux/i386), ensures that the user cannot

?????????????create? an?unlimited?number of zero-lengthmessages (such mes‐

?????????????sages nevertheless each consumesome system memory for bookkeep‐

?????????????ing overhead).

RLIMIT_NICE (since Linux 2.6.12, but seeBUGS below)

?????????????Specifies? a?ceiling?to? which the process's nice value can be

?????????????raised using setpriority(2) ornice(2).? The actual ceiling?for

?????????????the? nice?value is calculated as 20 - rlim_cur.?(This strange‐

?????????????ness occurs because negative? numbers?cannot?be? specified?as

?????????????resource? limit?values, since they typically have special mean‐

?????????????ings.? For example, RLIM_INFINITY typically is thesame as -1.)

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??????RLIMIT_NOFILE

?????????????Specifies a value one greaterthan the maximum? file?descriptor

?????????????number? that?can be opened by this process.?Attempts (open(2),

?????????????pipe(2), dup(2), etc.)? to exceed this?limit?yield? the?error

?????????????EMFILE.?? (Historically,? this?limit?was named RLIMIT_OFILE on

?????????????BSD.)

RLIMIT_NPROC

?????????????The maximum number of processes(or, more? precisely?on?Linux,

?????????????threads) that can be created forthe real user ID of the calling

?????????????process.? Upon encountering this limit, fork(2)fails?with? the

?????????????error EAGAIN.

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??????RLIMIT_RSS

?????????????Specifies? the?limit?(in? pages) of the process's resident set

?????????????(the number of virtual pagesresident in RAM).? This?limit?has

?????????????effect only in Linux 2.4.x, x< 30, and there affects only calls

?????????????to madvise(2) specifyingMADV_WILLNEED.

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??????RLIMIT_RTPRIO (Since Linux 2.6.12, but see BUGS)

?????????????Specifies a ceiling on thereal-time priority that? may?be? set

?????????????for? this?process?using? sched_setscheduler(2)? and sched_set‐

?????????????param(2).

RLIMIT_RTTIME (Since Linux 2.6.25)

?????????????Specifies a limit (inmicroseconds) on the amount? of?CPU?time

?????????????that a process scheduled under areal-time scheduling policy may

?????????????consume without making a blockingsystem call.? For the?purpose

?????????????of this limit, each time aprocess makes a blocking system call,

?????????????the count of its consumed CPUtime is reset to? zero.??The?CPU

?????????????time? count?is not reset if the process continues trying to use

?????????????the CPU but is preempted, itstime slice expires,? or?it?calls

?????????????sched_yield(2).

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?????????????Upon reaching the softlimit, the process is sent a SIGXCPU sig‐

?????????????nal.? If the process catches or ignores this signaland?contin‐

?????????????ues consuming CPU time, thenSIGXCPU will be generated once each

?????????????second until the hard limit? is?reached,?at? which?point?the

?????????????process is sent a SIGKILL signal.

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?????????????The? intended?use?of this limit is to stop arunaway real-time

?????????????process from locking up thesystem.

RLIMIT_SIGPENDING (Since Linux 2.6.8)

?????????????Specifies the limit on the numberof signals that may be? queued

?????????????for? the real user ID of the calling process.?Both standard and

?????????????real-time signals are counted forthe purpose of? checking?this

?????????????limit.??However, the limit is enforced only forsigqueue(3); it

?????????????is always possible to use kill(2)to queue one instance? of? any

?????????????of the signals that are notalready queued to the process.

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??????RLIMIT_STACK

?????????????The? maximum size of the process stack, inbytes.?Upon reaching

?????????????this limit, a SIGSEGV signal isgenerated.? To handle this?sig‐

?????????????nal,? a?process?must employ an alternatesignal stack (sigalt‐

?????????????stack(2)).

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?????????????Since Linux 2.6.23, this limitalso? determines?the?amount? of

?????????????space used for the process'scommand-line arguments and environ‐

?????????????ment variables; for details, seeexecve(2).

prlimit()

??????The Linux-specific prlimit() system call combines and extends the func‐

??????tionality?of? setrlimit() and getrlimit().? It can be used to both set

??????and get the resource limits of an arbitrary process.

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??????The resource argument has the same meaning as for setrlimit() and getr‐

??????limit().

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??????If?the? new_limit argument is a not NULL, then therlimit structure to

??????which it points is used to set new values for the soft and hard?limits

??????for resource.?If the old_limitargument is a not NULL, then a success‐

??????ful call to prlimit() places the previous?soft?and? hard?limits?for

??????resource in the rlimit structure pointed to by old_limit.

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??????The?pid? argument specifies the ID of the process onwhich the call is

??????to operate.?If pid is 0, then thecall applies to the calling process.

??????To?set or get the resources of aprocess other than itself, the caller

??????must have the CAP_SYS_RESOURCE capability, or the real, effective,?and

??????saved set user IDs of the target process must match the real user ID of

??????the caller and the real, effective, and saved set group IDs of the tar‐

??????get process must match the real group ID of the caller.

案例說明：

#define _GNU_SOURCE

#define _FILE_OFFSET_BITS 64

#include<stdio.h>

#include<time.h>

#include<stdlib.h>

#include<unistd.h>

#include<sys/resource.h>

?

#define errExit(msg)do{perror(msg);exit(EXIT_FAILURE);} while(0)

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int main(int argc,char *argv[])

{

struct rlimit old, new;

??????????struct rlimit *newp;

??????????pid_t pid;

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??????????if (!(argc == 2 || argc == 4)) {

??????????????fprintf(stderr, "Usage: %s<pid> [<new-soft-limit> "

??????????????????????"<new-hard-limit>]\n", argv[0]);

??????????????exit(EXIT_FAILURE);

??????????}

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??????????pid = atoi(argv[1]);???????/* PIDof target process */

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??????????newp = NULL;

??????????if (argc == 4) {

??????????????new.rlim_cur = atoi(argv[2]);

??????????????new.rlim_max = atoi(argv[3]);

??????????????newp = &new;

??????????}

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??????????/* Set CPU time limit of target process; retrieve and display

?????????????previous limit */

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??????????if (prlimit(pid, RLIMIT_CPU, newp, &old) == -1)

??????????????errExit("prlimit-1");

??????????printf("Previous limits: soft=%lld; hard=%lld\n",

??????????????????(long long) old.rlim_cur,(long long) old.rlim_max);

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??????????/* Retrieve and display new CPU time limit */

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??????????if (prlimit(pid, RLIMIT_CPU, NULL, &old) == -1)

??????????????errExit("prlimit-2");

??????????printf("New limits: soft=%lld; hard=%lld\n",

??????????????????(long long) old.rlim_cur,(long long) old.rlim_max);

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exit(EXIT_FAILURE);

}

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