On Wed, 2018-10-31 at 12:41 +0100, Michal Hocko wrote: > On Wed 31-10-18 18:19:42, Miles Chen wrote: > > On Wed, 2018-10-31 at 11:15 +0100, Michal Hocko wrote: > > > On Wed 31-10-18 16:47:17, Miles Chen wrote: > > > > On Tue, 2018-10-30 at 09:15 +0100, Michal Hocko wrote: > > > > > On Tue 30-10-18 14:55:51, Miles Chen wrote: > > > > > [...] > > > > > > It's a real problem when using page_owner. > > > > > > I found this issue recently: I'm not able to read page_owner information > > > > > > during a overnight test. (error: read failed: Out of memory). I replace > > > > > > kmalloc() with vmalloc() and it worked well. > > > > > > > > > > Is this with trimming the allocation to a single page and doing shorter > > > > > than requested reads? > > > > > > > > > > > > I printed out the allocate count on my device the request count is <= > > > > 4096. So I tested this scenario by trimming the count to from 4096 to > > > > 1024 bytes and it works fine. > > > > > > > > count = count > 1024? 1024: count; > > > > > > > > It tested it on both 32bit and 64bit kernel. > > > > > > Are you saying that you see OOMs for 4k size? > > > > > yes, because kmalloc only use normal memor, not highmem + normal memory > > I think that's why vmalloc() works. > > Can I see an OOM report please? I am especially interested that 1k > doesn't cause the problem because there shouldn't be that much of a > difference between the two. Larger allocations could be a result of > memory fragmentation but 1k vs. 4k to make a difference really seems > unexpected. > You're right. I pulled out the log and found that the allocation fail is for order=4. I found that the if I do the read on the device, the read count is <= 4096; if I do the read by 'adb pull' from my host PC, the read count becomes 65532. (I'm working on a android device) The overnight test used 'adb pull' command, so allocation fail occurred because of the large read count and the arbitrary size allocation design of page_owner. That also explains why vmalloc() works. I did a test today, the only code changed is to clamp to read count to PAGE_SIZE and it worked well. Maybe we can solve this issue by just clamping the read count. count = count > PAGE_SIZE ? PAGE_SIZE : count; Here is the log: <4>[ 261.841770] (0)[2880:sync svc 43]sync svc 43: page allocation failure: order:4, mode:0x24040c0 <4>[ 261.841815]-(0)[2880:sync svc 43]CPU: 0 PID: 2880 Comm: sync svc 43 Tainted: G W O 4.4.146+ #16 <4>[ 261.841825]-(0)[2880:sync svc 43]Hardware name: Generic DT based system <4>[ 261.841834]-(0)[2880:sync svc 43]Backtrace: <4>[ 261.841844]-(0)[2880:sync svc 43][<c010d57c>] (dump_backtrace) from [<c010d7a4>] (show_stack+0x18/0x1c) <4>[ 261.841866]-(0)[2880:sync svc 43] r6:60030013 r5:c123d488 r4:00000000 r3:dc8ba692 <4>[ 261.841880]-(0)[2880:sync svc 43][<c010d78c>] (show_stack) from [<c0470b84>] (dump_stack+0x94/0xa8) <4>[ 261.841892]-(0)[2880:sync svc 43][<c0470af0>] (dump_stack) from [<c0236060>] (warn_alloc_failed+0x108/0x148) <4>[ 261.841905]-(0)[2880:sync svc 43] r6:00000000 r5:024040c0 r4:c1204948 r3:dc8ba692 <4>[ 261.841919]-(0)[2880:sync svc 43][<c0235f5c>] (warn_alloc_failed) from [<c023a284>] (__alloc_pages_nodemask+0xa08/0xbd8) <4>[ 261.841929]-(0)[2880:sync svc 43] r3:0000000f r2:00000000 <4>[ 261.841939]-(0)[2880:sync svc 43] r8:0000002f r7:00000004 r6:dbb7a000 r5:024040c0 <4>[ 261.841953]-(0)[2880:sync svc 43][<c023987c>] (__alloc_pages_nodemask) from [<c023a5fc>] (alloc_kmem_pages+0x18/0x20) <4>[ 261.841963]-(0)[2880:sync svc 43] r10:c0286560 r9:c027b348 r8:0000fff8 r7:00000004 <4>[ 261.841978]-(0)[2880:sync svc 43][<c023a5e4>] (alloc_kmem_pages) from [<c02573c0>] (kmalloc_order_trace+0x2c/0xec)
