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shmget.2: Rework the SHMALL description 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2014-05-03 14:53:06 +02:00
parent 1fabbf12f6
commit d4bf702fac
1 changed files with 8 additions and 8 deletions
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man2/shmget.2
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@ -283,12 +283,14 @@ The following limits on shared memory segment resources affect the
call:
.TP
.B SHMALL
System-wide limit on the number of shared memory pages.
System-wide limit on the number of
.I pages
of shared memory.
Since Linux 3.17, the default value is nearly ULONG_MAX, which
effectively allows unlimited allocations.
From Linux 2.4 up to
Linux 3.16, the default value for this limit was
From Linux 2.4 up to Linux 3.16,
the default value for this limit was:
SHMMAX / PAGE_SIZE * (SHMMNI / 16)
@ -296,11 +298,9 @@ If
.B SHMMAX
and
.B SHMMNI
were not modified, this yielded in a limit for the
total memory used by all shared memory segments of 8 GB:
with a 4kB page size, this formula yields the value 2^21 (2,097,152);
with 8kB page size, it yields 2^20 (1048576).
were not modified, then multiplying the result of this formula
by the page size (to get a value in bytes) yielded a value of 8 GB
as the limit on the total memory used by all shared memory segments.
On Linux, this limit can be read and modified via
.IR /proc/sys/kernel/shmall .
.TP