See http://marc.info/?l=linux-mm&m=142122902313315&w=2 for more information.
On Mon 19-01-15 14:17:43, long.wanglong wrote: > Hi all: > > In the latest kernel, i set the memory limit (4096) in a test cgroup. and add > the test task. > the test code code is: > > testcase 1: mmap with MAP_LOCKED flag(memsize = 8192) > > 185 p = mmap(NULL, memsize, PROT_WRITE | PROT_READ, > 186 MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED, 0, 0); > 187 if (p == MAP_FAILED) > 188 err(1, "mmap(lock) failed"); > > expect: invoke OOM killer. > result: not invoke OOM killer. > > > testcase 2: mmap without MAP_LOCKED flag and the call mlock (memsize = 8192) > > 185 p = mmap(NULL, memsize, PROT_WRITE | PROT_READ, > 186 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); > 187 if (p == MAP_FAILED) > 188 err(1, "mmap(lock) failed"); > 189 > 190 if (mlock(p, memsize) == -1) > 191 err(1, "mlock failed") > > expect: invoke OOM killer. > result: invoke OOM killer. > > in the Linux Programmer's Manual: > > MAP_LOCKED (since Linux 2.5.37) > Lock the pages of the mapped region into memory in the manner > of mlock(2). This flag is ignored in older kernels. > > and > mlock() locks pages in the address range starting at addr and > continuing for len bytes. All pages that contain a part of the > specified address range are guaranteed to be resident in RAM when the > call returns successfully; the pages are guaranteed to stay in RAM > until later unlocked. > > According to the description in the manual, the two testcases are equivalent. > > why the first testcase does not invoke OOM killer? > does the mmap with MAP_LOCKED flag will not immediately allocate physical > memory? > > > Best Regards > Wang Long > -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
