system config ipc

System Config IPC

Iris Zhuiris.zhu@sun.com

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Agenda

• IPC Overview• System V IPC• Posix IPC• Tools for performance analysis• System configuration• Hands On Lab

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Process overview

ConceptExecution of programFundamental abstraction of unix systemBasic unit

ProcessVirtual memory environmentResource for ProcessMemoryOpen file listThread

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Conceptual view of a Process

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Process virtual address space

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IPC history

• Message passing> Pipe,named pipe(FIFO)> System V message queue> Posix message queue(1003.1b-1993)> RPC

• Data synchronization> System V semaphore,System V shared memory> Posix semaphore

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Inter Process Communication

FunctionSharing of data

shared memoryExchange Information and data

Pipe,FIFO,message queuesSynchronization of access to shared resources

semaphore,mutex,lock,Remote procedure call

Sun RPC,Solaris Door

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Unix Processes share data

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IPC object persistence

• Process-persistent> Pipe> FIFO

• Kernel persistent> System V Shared memory> System V Message queue> System V Semaphore

• Filesystem persistent

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Pipe

• Special type of file that do not hold data but can be opened by 2 different processed so that data can be passed between them.

• API> Int pipe(int fd[2]);> Fd[0] – read Fd[1] – write //For example:

• Feature> Half duplex.> Atomic operation.> Usable between processes with the same parent.

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Named pipe - FIFO

• Provide a bidirectional communication path between processed on the same system.

• API> Int mkfifo(const char *pathname,mode_t mode);> fopen/fclose //For example:

• Features> Half duplex> Automatic block> SIGPIPE is generated if a process write to a pipe and

read is terminated> Atomic operation

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System limitation -<limits.h>

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Other commands to get system variables

• limit(csh)/unlimit(sh/bash/ksh)• Sysdef

> lists all hardware devices, as well as pseudo devices, system devices, loadable modules, and the values of selected kernel tunable parameters.

> For example,sysdef(1M) //For exercise:• Getconf

> get configuration values> For example,getconf(1)

>getconf OPEN_MAX //For exercise:

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Doors• Provide a facility for processes to issue procedure

calls to functions in other processes running on the same system. //Sun Solaris OS

• Overview

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Agenda

• IPC Overview• System V IPC*• Posix IPC• Tools for performance analysis• System configuration• Hands On Lab

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System V IPC OverviewTypesSystem V shared memorySystem V message queuesSystem V semaphore

API

Shared memory Message Queue SemaphoreHeader file <sys/shm.h> <sys/msg.h> <sys/sem.h>Create/Open API Shmget Msgget SemgetManagement API Shmctl Msgctl SemctlOperation API Shmat Msgsnd Semop

Shmdt Msgrcv

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System V IPC overview

key_t and ftok #include <sys/ipc.h>key_t ftok (const char * pathname,int id);

Create and open IPCkey=id(8bit)+st_dev(12bit)+st_ino(12bit)

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Data structure in kernel for IPC

• ipc_perm data structure in /usr/include/sys/ipc.h

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System V shared memory

Conceptsharing the same physical(RAM) memorypages by multi processes

FeatureExtremely efficient(*)Dynamically loaded when required,eg.modloadUnload when system reboot or by command modunload

Kernel resource consumptionShmid

actual shared RAM pages data structure about the shared segment

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System V shared memory - API

• Header file and system calls #include <sys/types.h>

#include <sys/ipc.h>

#include <sys/shm.h>

int shmget(key_t key, size_t size, int shmflg);void *shmat(int shmid, const void *shmaddr, int shmflg);int shmctl(int shmid, int cmd, struct shmid_ds *buf);int shmdt(char *shmaddr);

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Data structure

Struct shmid_ds{

struct ipc_perm shm_perm /* operation permission structure */size_t shm_segsz /* size of segment in bytes */pid_t shm_lpid /* process ID of last shared memory operation */pid_t shm_cpid /* process ID of creator */shmatt_t shm_nattch /* number of current attaches */time_t shm_atime /* time of last shmat() */time_t shm_dtime /* time of last shmdt() */time_t shm_ctime /* time of last change by shmctl() */}

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Example,process with shared memory

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System overheads with shared memory

User levelQuantity of created shared memorySize

Kernel levelSystem memory

Quantity of identifiersMax size for shared memory segment Translation table of shared memorySwap space

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System tunable parameters

• System profile(before Solaris 10)> /etc/system

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Caveat

• Static mechanism• Values specified are read and applied when system boot.• Any changes are not applied until the system reboot• Values specified in /etc/system are global and affect all

processes on the system• The obsolete tunable settings are ignored from Solaris 10.

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Resource control available

• Dynamically resource control> Prctl(1)

> get or set the resource controls of running processes, tasks, and projects

> rctladm(1M)> display or modify global state of system resource controls

> Man resource_controls(5)> Setrctl(2)

> API,set or get resource control values> Man rctlblk_get_local_action(3C)

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Dynamic resource control

Settings in Solaris 10

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Obsolete tunable parameter

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Example

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Optimization of shared memory - ISM

Concept ISM - Intimate shared memorySharing of the translation tables involved in

virtual-to-physical address translationNo need to share the actual physical memory

pages

ContrastNon-ISM

per-processes mapping for shared memory pages

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Background introduction – memory basic

MMU - Virtual memory management unit Management and translation of the virtual view

of memory(address space) to physical memory.

HAT - Hardware address translation layer Management mapping of virtual to physical

memory

TLB - Translation lookaside buffer Hardware cache of recent address translation

information

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Hardware address translation

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ISM

Sharing the memory translation table

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Non-ISM

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FeatureAvoid generate redundant mappings to physical pages Intimate shared memory is an important optimization that makes more efficient use of the kernel and hardware resources involved in the implementation of virtual memory and provides a means of keeping heavily used shared pages locked in memory.

Large page size automatically enabled

ISM

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Example - ISM used for Database

Without ISM400 database processes2GB shared segment ~262144 8KB pages

8Bytes for each page mapping-->2M2M*400

➔ 800Mbytes for mapping!

With ISM➔ 2Mbytes only.

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System V message queues

ConceptFor process to send and receive messages in

various size in an asynchronous fashion.

FeatureDramatical loadable moduleDepends on /kernel/sys/msgsys /kernel/misc/ipc

Kernel resource consumption Kernel memoryResource map

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System V IPC - message queue API

• Header file and system calls#include <sys/msg.h>int msgget(key_t key, int msgflg);int msgctl(int msqid, int cmd, struct msqid_ds *buf);int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);size_t msgrcv(int msqid, void *msgp, size_t msgsz, long int msgtyp,

int msgflg);

• More available from man page> e,g, man msg

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Data Structure Struct msqid_ds{

Struct ipc_perm msg_perm; /*read-write perms*/Struct msg msg_first; /ptr to first message on queue*/Struct msg *msg_last; /ptr to last message on queue*/msglen_t msg_cbytes;/*current #bytes on queue*/msgqnum_t msg_qnum; /*current #of messages on queue*/msglen_t msg_qbytes;/*max # of bytes allowed on queue*/pid_t msg_lspid; /*pid of last msgsnd()*/pid_t msg_lrpid; /*pid of last msgrcv()*/time_t msg_stime; /*time of last msgsnd()*/time_t msg_rtime; /*time of last msgrcv()*/time_t msg_ctime; /*pid of last msgctl()*/}

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System V message queues structures

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System overhead with message queues

Kernel memorycheck first,no greater than 25% available

kernel memory

Resource mapIdentifier msqid_ds sys/msg.h Struct msg

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System tunable parameter

/etc/system

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Available resource control

• process.max-msg-messages> msginfo_msgtql(obsolete)> maximum number of messages on a message queue

• process.max-msg-qbytes> msginfo_msgmnb(obsolete)> maximum number of bytes of messages on a message

queue• project.max-msg-ids

> msginfo_msgmni(obsolete)> maximum number of message queue Ids allowed for a

project

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System V SemaphoreConceptmechanical signaling device or a means of doing

visual signaling.A method of synchronizing to a sharable

resource by multi processes.

FeatureP – try or attempt; V – increaseSemaphore sets available

Kernel resource consumptionKernel memoryResource map

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System V IPC semaphore -API

• Header file and system calls#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>int semget(key_t key, int nsems, int semflg);int semctl(int semid, int semnum, int cmd, ...);int semop(int semid, struct sembuf *sops, size_t nsops);

• More available from man page> Man sem> e,g.semget(2)

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System V semaphore

• Binary semaphore> 0 or 1,like mutex

• Counting semaphore> 0~system limitation ,P/V

• Set of counting semaphores> One or more,each set has a limitation

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Data structures for semaphoreStruct semid_ds

Struct sem_buf

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System overhead with semaphoreKernel memory

Must less than 25% of kernel memory

Resource map allocationSem structure based on semmnsIdentifier semid_dsUndo structure pointerUndo structure themselvesKernel mutex lock

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System tunable parameter

/etc/system(part)

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System tunable parameter

/etc/system

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Available resource control

• process.max-sem-ops> seminfo_semopm(obsolete)> Maximum operations per semop(2) call

• process.max-sem-nsems> seminfo_semmsl(obsolete)> Maximum semaphores per identifiers

• project.max-sem-ids> seminfo_semmni(obsolete)> Number of semaphore identifiers

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Agenda

• IPC Overview• System V IPC• Posix IPC• Tools for performance analysis• System configuration• Hands On Lab

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Posix IPC Overview

TypesPosix message queuesPosix semaphorePosix shared memory API

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Posix IPC and System V IPC

• Common points Types/Function • Difference-Implementation

> Library – libposix4.so vs libc.so> Implementation> Built on Solaris file memory mapping interface

-- mmap(2) > acquired desired resource by using a file name

convention

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Difference with System V IPC

(continue...)> No APIs entering into kernel are executed > No tunable parameters are required> Limiting factors - Per-process limit

open files memory spaces

> Common routines _pos4obj _open/_pos4obj _name _open _nc/_close _nc _pos4obj _lock/_pos4obj _unlock

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mmapFunctionmapping a file or some other named objects into a

process's space address.

Achievement Common files used for memory reflectingSpecial files for anonymous memory reflectingshm_open for unallied processes shared memory

API #include <sys/mman.h> void *mmap(void *addr,size_t len,int prot,int

flags,int fd,off_t offset);

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Process address space with mmap(2)

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Posix Semaphores

• Named semaphore> sem_open()/sem_close()/sem_unlink

• Unnamed semaphore(memory based)> sem_init()/sem_destroy

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System-imposed limits

• <unistd.h>• SEM_NSEMS_MAX

> Maximum number of semaphores per process• SEM_VALUE_MAX

> Maximum value of a semaphore> e,g. #getconf -a|grep SEM

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Posix message queue

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Posix message queue

• System limits in /usr/include/limits.h> MQ_OPEN_MAX> MQ_PRIO_MAX> e,g getconf -a |grep MQ

• Tunable parameters> mq_open(3R)> mq_setattr(3R)

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Agenda

• Solaris multi-thread process• Inter-processes IPC• System V IPC• Posix IPC• Tools for performance analysis• System configuration• Hands On Lab

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Performance analysis process

• Understand the problem. • Collect data with tools for performance analysis.

> iostat,kstat,mdb,pmap,vmstat,ps,etc.> Proc tools> Dtrace> Sun studio11

• Separate all the data you get from different layers.> CPU> Memory > System I/O> File system> ...

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Performance tuning process

•Find the area and the period of the bottleneck.•Set up performance goal.•Performance tuning

> E,g. Resource control with IPC.•Review and repeat until meet tuning goals .•Report with comparison available.

•Tools for performance analysis related to IPC

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kmstat(1M)

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vmstat(1M)

• Rports virtual memory statistics regarding kernel thread, virtual memory, disk, trap, and CPU activity.> memory-report on usage of virtual and real memory> mf-minor faults> pi- kilobytes paged in> po- kilobytes paged out

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pmap -x(1M)

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Pmap -x example

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ipcs(1M)

• report inter-process communication facilities status> -m active shared memory segments.> -q active message queues.> -s active semaphores.> -i number of ISM attaches to shared memory

segments.> -p process number> -A all print options, -b, -c, -i, -J, -o, -p, and -t.> -z information about facilities associated with the

specified zone > -Z information about all zones

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ipcrm(1)

• Remove a message queue, semaphore set, or shared memory ID> -m shmid > -q msqid > -s semid> -M shmkey > -Q msgkey > -S semkey> -z zone

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dtrace(1M)

• Comprehensive dynamic tracing framework for the Solaris Operating system.> Powerful infrastructure to permit administrators,developers

to understanding behavior of the operating system and user processes.

• Observe the system call related to ipc> fbt provider provides probe into every function in the

kernel > shmsys provider provides probe into system API with ipc> ipc module,probe related to ipc in kernel

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Sun Studio- Performance analyzer

• Combination of compiler,libraries of optimized functions and tools for performance analysis.

• Command and sub-command> er_print-- generate a plain-text report of performance

data> Collect – simplest interface for collecting data> Dbx collector – performance analyzing for active process> Analyzer – GUI tool

> #collect -L unlimited -A copy -F on -d /tmp/a.out ->/tmp/test.1.er> #analyzer test.1.er

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Agenda

• Solaris multi-thread process• Inter-processes IPC• System V IPC• Posix IPC• Tools for performance analysis• System configuration• Hands On Lab

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System configuration

• How to modify kernel parameters?> Modify the /etc/system> Use the kernel debugger(kmdb)> Use the modular debugger(Mdb)> Use the ndd command to set TCP/IP parameters> Modify the /etc/default files

• Viewing Solaris system configuration information> Sysdef(1M) command> Kstat(1M) or Kstat(3Kstat)

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Example

• Setting a parameter in /etc/system> Set nfs:nfs_nra=4(read-ahead blocks that are read for

file system mounted using NFS version 2 software)• Using mdb to change a value

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Sysdef command

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Reference

• Solaris Internal• Unix Network Programming Vol II• Solaris Dynamic Tracing Guide• Solaris Modular Debugger Guide• Solaris Tunable Parameters Reference Manual

Iris Zhuiris.zhu@sun.com

System Config IPC