Introduction to Semaphores ma Linux

Ua hoʻomākaukau ʻia ka unuhi ʻana o ka ʻatikala ma ka pō o ka hoʻomaka ʻana o ka papa "Ka Luna Hoʻokele Linux.Basic".

ʻO ka semaphore kahi hana e hiki ai i nā kaʻina hoʻokūkū a me nā kaula ke kaʻana like i nā kumuwaiwai a kōkua i nā pilikia hoʻonohonoho like ʻole e like me nā lāhui, nā paʻa (paʻa paʻa), a me nā kaula kolohe.

No ka hoʻoponopono i kēia mau pilikia, hāʻawi ka kernel i nā mea hana e like me mutexes, semaphores, hōʻailona, ​​​​a me nā pale.

ʻEkolu ʻano o nā semaphore:

1. Semaphore binary
2. Semaphores-counters (helu helu semaphore)
3. Nā pūʻulu o nā semaphores (semaphore set)

Nānā i ke kūlana IPC

Hāʻawi kēia mau kauoha i ka ʻike e pili ana i ke kūlana o kēia manawa o ke kamaʻilio inter-process (IPC).

# ipcs
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 65536 root 600 393216 2 dest
0x00000000 98305 root 600 393216 2 dest
0x00000000 131074 root 600 393216 2 dest
0x00000000 163843 root 600 393216 2 dest
0x00000000 196612 root 600 393216 2 dest
0x00000000 229381 root 600 393216 2 dest
0x00000000 262150 root 600 393216 2 dest
0x00000000 294919 root 600 393216 2 dest
0x00000000 327688 root 600 393216 2 dest
------ Semaphore Arrays --------

key semid owner perms nsems

------ Message Queues --------
key msqid owner perms used-bytes messages

Nā papa hana o nā semaphore

Hōʻike i ka ʻike e pili ana i nā papa hana semaphore.

# ipcs -s
------ Semaphore Arrays --------
key semid owner perms nsems

Māhele hoʻomanaʻo like

Nānā i ka ʻike e pili ana i nā ʻāpana hoʻomanaʻo kaʻana like.

# ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 65536 root 600 393216 2 dest
0x00000000 98305 root 600 393216 2 dest

Nā palena

hui ipcs -l hōʻike i ka hoʻomanaʻo like, semaphore, a me nā palena memo.

# ipcs -l
------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 4194303
max total shared memory (kbytes) = 1073741824
min seg size (bytes) = 1

------ Semaphore Limits --------
max number of arrays = 128
max semaphores per array = 250
max semaphores system wide = 32000
max ops per semop call = 32
semaphore max value = 32767

------ Messages: Limits --------
max queues system wide = 16
max size of message (bytes) = 65536
default max size of queue (bytes) = 65536

Hoʻomanaʻo like

Hōʻike ke kauoha ma lalo i ka hoʻomanaʻo like.

# ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0x00000000 65536 root 600 393216 2 dest
0x00000000 98305 root 600 393216 2 dest
0x00000000 131074 root 600 393216 2 dest
0x00000000 163843 root 600 393216 2 dest
0x00000000 196612 root 600 393216 2 dest
0x00000000 229381 root 600 393216 2 dest
0x00000000 262150 root 600 393216 2 dest
0x00000000 294919 root 600 393216 2 dest
0x00000000 327688 root 600 393216 2 dest

Nā mea hana waiwai

Hōʻike ke kauoha i ka mea hoʻohana a me ka hui o ka mea nona a me ka mea nāna i hana i ka waiwai.

# ipcs -m -c

------ Shared Memory Segment Creators/Owners --------
shmid perms cuid cgid uid gid
65536 600 root root root root
98305 600 root root root root
131074 600 root root root root
163843 600 root root root root
196612 600 root root root root
229381 600 root root root root
262150 600 root root root root
294919 600 root root root root
327688 600 root root root root

Ke hoʻohana nei i nā mea hana IPC

Ma ka laʻana ma lalo nei, ka palena -u hōʻike i kahi hōʻuluʻulu o ka hoʻohana ʻana i nā mea hana IPC āpau.

# ipcs -u

------ Shared Memory Status --------
segments allocated 9
pages allocated 864
pages resident 477
pages swapped 0
Swap performance: 0 attempts 0 successes

------ Semaphore Status --------
used arrays = 0
allocated semaphores = 0

------ Messages: Status --------
allocated queues = 0
used headers = 0
used space = 0 bytes

Ke pau nā lawelawe, pono e holoi ʻia nā semaphore a me nā ʻāpana hoʻomanaʻo like. Inā ʻaʻole i wehe ʻia, a laila hiki ke hana i kēia me ka hoʻohana ʻana i ke kauoha ipcrm, e hoʻohele i ka mea ʻike o ka mea IPC.

# ipcs -a
# ipcrm -s < sem id>

Hiki iā ʻoe ke hoʻololi i nā palena semaphore me ka hoʻohana ʻana sysctl.

# /sbin/sysctl -w kernel.sem=250

Source: www.habr.com