(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Sat, 29 Dec 2018 09:00:22 +0000 bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=202089 > > Bug ID: 202089 > Summary: transparent hugepage not compatable with > madvise(MADV_DONTNEED) > Product: Memory Management > Version: 2.5 > Kernel Version: 4.4.0-117 > Hardware: x86-64 > OS: Linux > Tree: Mainline > Status: NEW > Severity: high > Priority: P1 > Component: Other > Assignee: akpm@xxxxxxxxxxxxxxxxxxxx > Reporter: jianpanlanyue@xxxxxxx > Regression: No > > environment: > 1.kernel 4.4.0 on x86_64 > 2.echo always > /sys/kernel/mm/transparent_hugepage/enable > echo always > /sys/kernel/mm/transparent_hugepage/defrag > echo 2000000 > /sys/kernel/mm/transparent_hugepage/khugepaged/pages_to_scan > ( faster defrag pages to reproduce problem) > > problem: > 1. use mmap() to allocate 4096 bytes for 1024*512 times (4096*1024*512=2G). > 2. use madvise(MADV_DONTNEED) to free most of the above pages, but reserve a > few pages(by if（i%33==0) continue;), then process's physical memory firstly > come down, but after a few seconds, it rise back to 2G again, and can't come > down forever. > 3. if i delete this condition(if（i%33==0) continue;) or disable > transparent_hugepage by setting 'enable' and 'defrag' to never, all go well and > the physical memory can come down expectly. > > It seems like transparent_hugepage has problems with non-contiguous > madvise(MADV_DONTEED). > > > Belows is the test code: > > #include <stdio.h> > #include <memory.h> > #include <stdlib.h> > #include <sys/mman.h> > #include <errno.h> > #include <assert.h> > > #define PAGE_SIZE 4096 > #define PAGE_COUNT 1024*512 > int main() > { > void** table = (void**)malloc(sizeof(void*) * PAGE_COUNT); > printf("begin mmap...\n"); > > for (int i=0; i<PAGE_COUNT; i++) { > table[i] = mmap(NULL, PAGE_SIZE, PROT_READ|PROT_WRITE, > MAP_PRIVATE|MAP_ANONYMOUS, -1 ,0); > assert(table[i] != MAP_FAILED); > memset(table[i], 1, PAGE_SIZE); > } > > printf("mmap ok, press enter to free most of them\n"); > getchar(); > > //it behaves not expectly: after most pages freed, thp make it rise to 2G > again > for(int i=0; i<PAGE_COUNT; i++) { > if (i%33==0) continue; > if (madvise(table[i], PAGE_SIZE, MADV_DONTNEED) != 0) > printf("madvise error, errno:%d\n", errno); > } > > printf("munmap finish\n"); > free(table); > getchar(); > getchar(); > } > > -- > You are receiving this mail because: > You are the assignee for the bug.
