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Fri, 13 Sep 2019 04:17:52 -0700 (PDT) MIME-Version: 1.0 References: <20190912231820.590276-1-lucian@fb.com> In-Reply-To: <20190912231820.590276-1-lucian@fb.com> From: Souptick Joarder Date: Fri, 13 Sep 2019 16:47:40 +0530 Message-ID: Subject: Re: [PATCH] mm: memory: fix /proc/meminfo reporting for MLOCK_ONFAULT To: Lucian Adrian Grijincu Cc: Linux-MM , linux-kernel@vger.kernel.org, Michal Hocko , Andrew Morton , Rik van Riel , Roman Gushchin Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 13, 2019 at 4:49 AM Lucian Adrian Grijincu wrote: > > As pages are faulted in MLOCK_ONFAULT correctly updates > /proc/self/smaps, but doesn't update /proc/meminfo's Mlocked field. > > - Before this /proc/meminfo fields didn't change as pages were faulted in: > > ``` > = Start = > /proc/meminfo > Unevictable: 10128 kB > Mlocked: 10132 kB > = Creating testfile = > > = after mlock2(MLOCK_ONFAULT) = > /proc/meminfo > Unevictable: 10128 kB > Mlocked: 10132 kB > /proc/self/smaps > 7f8714000000-7f8754000000 rw-s 00000000 08:04 50857050 /root/testfile > Locked: 0 kB > > = after reading half of the file = > /proc/meminfo > Unevictable: 10128 kB > Mlocked: 10132 kB > /proc/self/smaps > 7f8714000000-7f8754000000 rw-s 00000000 08:04 50857050 /root/testfile > Locked: 524288 kB > > = after reading the entire the file = > /proc/meminfo > Unevictable: 10128 kB > Mlocked: 10132 kB > /proc/self/smaps > 7f8714000000-7f8754000000 rw-s 00000000 08:04 50857050 /root/testfile > Locked: 1048576 kB > > = after munmap = > /proc/meminfo > Unevictable: 10128 kB > Mlocked: 10132 kB > /proc/self/smaps > ``` > > - After: /proc/meminfo fields are properly updated as pages are touched: > > ``` > = Start = > /proc/meminfo > Unevictable: 60 kB > Mlocked: 60 kB > = Creating testfile = > > = after mlock2(MLOCK_ONFAULT) = > /proc/meminfo > Unevictable: 60 kB > Mlocked: 60 kB > /proc/self/smaps > 7f2b9c600000-7f2bdc600000 rw-s 00000000 08:04 63045798 /root/testfile > Locked: 0 kB > > = after reading half of the file = > /proc/meminfo > Unevictable: 524220 kB > Mlocked: 524220 kB > /proc/self/smaps > 7f2b9c600000-7f2bdc600000 rw-s 00000000 08:04 63045798 /root/testfile > Locked: 524288 kB > > = after reading the entire the file = > /proc/meminfo > Unevictable: 1048496 kB > Mlocked: 1048508 kB > /proc/self/smaps > 7f2b9c600000-7f2bdc600000 rw-s 00000000 08:04 63045798 /root/testfile > Locked: 1048576 kB > > = after munmap = > /proc/meminfo > Unevictable: 176 kB > Mlocked: 60 kB > /proc/self/smaps > ``` > > Repro code. > --- > > int mlock2wrap(const void* addr, size_t len, int flags) { > return syscall(SYS_mlock2, addr, len, flags); > } > > void smaps() { > char smapscmd[1000]; > snprintf( > smapscmd, > sizeof(smapscmd) - 1, > "grep testfile -A 20 /proc/%d/smaps | grep -E '(testfile|Locked)'", > getpid()); > printf("/proc/self/smaps\n"); > fflush(stdout); > system(smapscmd); > } > > void meminfo() { > const char* meminfocmd = "grep -E '(Mlocked|Unevictable)' /proc/meminfo"; > printf("/proc/meminfo\n"); > fflush(stdout); > system(meminfocmd); > } > > { \ > int rc = (call); \ > if (rc != 0) { \ > printf("error %d %s\n", rc, strerror(errno)); \ > exit(1); \ > } \ > } > int main(int argc, char* argv[]) { > printf("= Start =\n"); > meminfo(); > > printf("= Creating testfile =\n"); > size_t size = 1 << 30; // 1 GiB > int fd = open("testfile", O_CREAT | O_RDWR, 0666); > { > void* buf = malloc(size); > write(fd, buf, size); > free(buf); > } > int ret = 0; > void* addr = NULL; > addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); > > if (argc > 1) { > PCHECK(mlock2wrap(addr, size, MLOCK_ONFAULT)); > printf("= after mlock2(MLOCK_ONFAULT) =\n"); > meminfo(); > smaps(); > > for (size_t i = 0; i < size / 2; i += 4096) { > ret += ((char*)addr)[i]; > } > printf("= after reading half of the file =\n"); > meminfo(); > smaps(); > > for (size_t i = 0; i < size; i += 4096) { > ret += ((char*)addr)[i]; > } > printf("= after reading the entire the file =\n"); > meminfo(); > smaps(); > > } else { > PCHECK(mlock(addr, size)); > printf("= after mlock =\n"); > meminfo(); > smaps(); > } > > PCHECK(munmap(addr, size)); > printf("= after munmap =\n"); > meminfo(); > smaps(); > > return ret; > } > > --- > > Signed-off-by: Lucian Adrian Grijincu > --- > mm/memory.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index e0c232fe81d9..7e8dc3ed4e89 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3311,6 +3311,9 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, > } else { > inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page)); > page_add_file_rmap(page, false); > + if ((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED && > + !PageTransCompound(page)) Do we need to check against VM_SPECIAL ? > + mlock_vma_page(page); > } > set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); > > -- > 2.17.1 > >