The test program: /* * This test aims to provoke VHPT misses. * * In order to maximize the number of the TLB entries needed for the virtually mapped * PTE pages, only one valid PTE / page will be used (, and a single byte per data page). * The TLB pressure will me multiplied by "N" in order not to leave any * practical chance for a TLB hit. * * Remember to allow to over-commit memory: "sysctl -w vm.overcommit_memory=1". * * ...there is no control over the physical addresses of the user pages... there will * be some variation of the results from run to run due to some address aliases... * * ...the interrupts are enabled... */ #include <sys/types.h> #include <stdio.h> #include <sys/mman.h> #define N 8 // TLB pressure multiplier #define N_RUNS 10 #define N_EXTERNAL_LOOPS 10 #define N_INTERNAL_LOOPS 1000 #define CACHE_BYTES 128 #define N_TLB_ENTRIES 128 // Not counting the kernel's DTRs... #define N_PTE_PAGE_U_PAGE_PAIRS (N_TLB_ENTRIES / 2 * N) #define PTE_PER_CACHE_BYTES (CACHE_BYTES / sizeof(unsigned long)) unsigned int pagesize; #define PTES_PER_PAGE (pagesize / sizeof(void *)) #define VA_RANGE_PER_PTE_PAGE (PTES_PER_PAGE * pagesize) /* * Cache line "coloring" in order to reduce cache alias problems. * (Yet as there is no control over the physical addresses of the user pages...) * The i-th element touched by the innermost loop will be at the offset in the page: * (i * 2 + 1) * CACHE_BYTES * The PTE mapping this test data will be at the offset in its page: * i * 2 * CACHE_BYTES */ #define OFFSET (VA_RANGE_PER_PTE_PAGE + \ 2 * PTE_PER_CACHE_BYTES * pagesize + \ 2 * CACHE_BYTES) unsigned int offset; #define TEST_VA_RANGE ((unsigned long) VA_RANGE_PER_PTE_PAGE * \ N_PTE_PAGE_U_PAGE_PAIRS + \ /* Cache line "coloring": */ \ 2 * N_PTE_PAGE_U_PAGE_PAIRS * \ PTE_PER_CACHE_BYTES * pagesize + \ 2 * N_PTE_PAGE_U_PAGE_PAIRS * CACHE_BYTES) #define MEM_PROT (PROT_READ | PROT_WRITE) #define MEM_TYPE (MAP_PRIVATE | MAP_ANONYMOUS) #define GET_ITC() \ ({ \ unsigned long ia64_intri_res; \ \ asm volatile ("mov %0=ar.itc" : "=r"(ia64_intri_res)); \ ia64_intri_res; \ }) inline unsigned long test(char *p0, unsigned int n) { int i, j; char *p; unsigned long itc0 = GET_ITC(); for (j = 0; j < n; j++) for (i = 0, p = p0 + CACHE_BYTES; // Cache line "coloring" i < N_PTE_PAGE_U_PAGE_PAIRS; i++, p += offset) *p = i; return GET_ITC() - itc0; } void main_test(void) { void *p; int loop; unsigned long tmp, sum = 0; p = mmap(NULL, TEST_VA_RANGE, MEM_PROT, MEM_TYPE, -1, 0); if (p == MAP_FAILED){ perror("mmap"); fprintf(stderr, "Have you allowed to over-commit memory? " "Try: \"sysctl -w vm.overcommit_memory=1\"\n"); exit(1); } (void) test(p, 1); // Warm up... for (loop = 0; loop < N_EXTERNAL_LOOPS; loop++) sum += test(p, N_INTERNAL_LOOPS); (void) munmap(p, TEST_VA_RANGE); printf("ITC ticks: %ld,%03ld,%03ld,", sum / 1000000, sum / 1000 % 1000, sum % 1000); tmp = (unsigned long) N_EXTERNAL_LOOPS * N_INTERNAL_LOOPS * N_PTE_PAGE_U_PAGE_PAIRS; printf(" # user accesses: %ld,%03ld,%03ld, ITC ticks / access: %ld\n", tmp / 1000000, tmp / 1000 % 1000, tmp % 1000, sum / tmp); } int main(int argc, char *argv[]) { int run; unsigned long tmp; pagesize = getpagesize(); offset = OFFSET; // Depends on "getpagesize()" printf("Page size =\t\t\t%12d\n", pagesize); printf("PTEs / page =\t\t\t%12d\n", PTES_PER_PAGE); printf("VA range / PTE page =\t\t%12d (%d Mbytes)\n", VA_RANGE_PER_PTE_PAGE, VA_RANGE_PER_PTE_PAGE >> 20); printf("# PTE-page / user-page pairs =\t%12d\n", N_PTE_PAGE_U_PAGE_PAIRS); printf("Test VA range =\t\t\t%12ld (%ld Gbytes)\n", TEST_VA_RANGE, TEST_VA_RANGE >> 30); tmp = N_PTE_PAGE_U_PAGE_PAIRS * pagesize; printf("Resident user memory =\t\t%12ld (%ld Mbytes)\n", tmp, tmp >> 20); printf("# PTE + user cache lines =\t%12d (%d Kbytes)\n", N_PTE_PAGE_U_PAGE_PAIRS * 2, N_PTE_PAGE_U_PAGE_PAIRS * 2 * CACHE_BYTES >> 10); printf("\n"); for (run = 0; run < N_RUNS; run++) main_test(); return 0; } - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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