Maximum number of shared memory segments limited to 32767 in the kernel. why ?.

https://access.redhat.com/solutions/59416

 SOLUTION 已验证 - 已更新 2016年四月1日01:43 - 

English 

环境

• Red Hat Enterprise Linux 4, 5, 6, and 7

问题

• Maximum number of shared memory segments limited to 32767 in the kernel. why ?
• Increase /proc/sys/kernel/shmmni to more than 32768
• When the number of segments reaches 32767 shmget gives:

Raw

error 28 (no space left on device)

决议

From kernel source file include/linux/ipc.h  there is a restriction for 32768.

Raw

#define IPCMNI 32768  /* <= MAX_INT limit for ipc arrays (including sysctl changes) */

诊断步骤

Build kernel with below changes:

Raw

--- linux-2.6.18/include/linux/ipc.h     2006-09-20 09:12:06.000000000 +0530
+++ linux-2.6.18/include/linux/rruban-ipc.h     2011-07-12 12:53:58.000000000 +0530
@@ -51,7 +51,7 @@ struct ipc_perm

#ifdef __KERNEL__

-#define IPCMNI 32768  /* <= MAX_INT limit for ipc arrays (including sysctl changes) */
+#define IPCMNI 45000  /* <= MAX_INT limit for ipc arrays (including sysctl changes) */

/* used by in-kernel data structures */
struct kern_ipc_perm

By changing it to 45000, you areable to allocate more than 32768 shared memory segments.

Raw

>   
> # ./shmtest  
> Allocating segment nshmget: Success  
> Allocating segment no 43000

There is a limitation of 32768 currently with all versions of RHEL and upstream Linux.

 

相关的参考文章：https://blog.youkuaiyun.com/msdnchina/article/details/80641613