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101 lines
2.5 KiB
101 lines
2.5 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* hugepage-shm: |
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* |
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* Example of using huge page memory in a user application using Sys V shared |
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* memory system calls. In this example the app is requesting 256MB of |
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* memory that is backed by huge pages. The application uses the flag |
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* SHM_HUGETLB in the shmget system call to inform the kernel that it is |
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* requesting huge pages. |
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* |
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* For the ia64 architecture, the Linux kernel reserves Region number 4 for |
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* huge pages. That means that if one requires a fixed address, a huge page |
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* aligned address starting with 0x800000... will be required. If a fixed |
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* address is not required, the kernel will select an address in the proper |
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* range. |
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* Other architectures, such as ppc64, i386 or x86_64 are not so constrained. |
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* |
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* Note: The default shared memory limit is quite low on many kernels, |
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* you may need to increase it via: |
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* |
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* echo 268435456 > /proc/sys/kernel/shmmax |
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* |
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* This will increase the maximum size per shared memory segment to 256MB. |
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* The other limit that you will hit eventually is shmall which is the |
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* total amount of shared memory in pages. To set it to 16GB on a system |
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* with a 4kB pagesize do: |
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* |
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* echo 4194304 > /proc/sys/kernel/shmall |
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*/ |
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#include <stdlib.h> |
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#include <stdio.h> |
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#include <sys/types.h> |
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#include <sys/ipc.h> |
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#include <sys/shm.h> |
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#include <sys/mman.h> |
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#ifndef SHM_HUGETLB |
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#define SHM_HUGETLB 04000 |
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#endif |
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#define LENGTH (256UL*1024*1024) |
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#define dprintf(x) printf(x) |
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/* Only ia64 requires this */ |
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#ifdef __ia64__ |
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#define ADDR (void *)(0x8000000000000000UL) |
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#define SHMAT_FLAGS (SHM_RND) |
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#else |
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#define ADDR (void *)(0x0UL) |
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#define SHMAT_FLAGS (0) |
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#endif |
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int main(void) |
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{ |
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int shmid; |
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unsigned long i; |
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char *shmaddr; |
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shmid = shmget(2, LENGTH, SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W); |
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if (shmid < 0) { |
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perror("shmget"); |
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exit(1); |
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} |
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printf("shmid: 0x%x\n", shmid); |
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shmaddr = shmat(shmid, ADDR, SHMAT_FLAGS); |
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if (shmaddr == (char *)-1) { |
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perror("Shared memory attach failure"); |
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shmctl(shmid, IPC_RMID, NULL); |
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exit(2); |
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} |
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printf("shmaddr: %p\n", shmaddr); |
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dprintf("Starting the writes:\n"); |
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for (i = 0; i < LENGTH; i++) { |
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shmaddr[i] = (char)(i); |
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if (!(i % (1024 * 1024))) |
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dprintf("."); |
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} |
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dprintf("\n"); |
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dprintf("Starting the Check..."); |
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for (i = 0; i < LENGTH; i++) |
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if (shmaddr[i] != (char)i) { |
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printf("\nIndex %lu mismatched\n", i); |
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exit(3); |
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} |
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dprintf("Done.\n"); |
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if (shmdt((const void *)shmaddr) != 0) { |
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perror("Detach failure"); |
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shmctl(shmid, IPC_RMID, NULL); |
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exit(4); |
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} |
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shmctl(shmid, IPC_RMID, NULL); |
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return 0; |
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}
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