Hi Joonsoo, On 2016/3/4 10:02, Joonsoo Kim wrote: > On Thu, Mar 03, 2016 at 08:49:01PM +0800, Hanjun Guo wrote: >> On 2016/3/3 15:42, Joonsoo Kim wrote: >>> 2016-03-03 10:25 GMT+09:00 Laura Abbott <labbott@xxxxxxxxxx>: >>>> (cc -mm and Joonsoo Kim) >>>> >>>> >>>> On 03/02/2016 05:52 AM, Hanjun Guo wrote: >>>>> Hi, >>>>> >>>>> I came across a suspicious error for CMA stress test: >>>>> >>>>> Before the test, I got: >>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>> CmaTotal: 204800 kB >>>>> CmaFree: 195044 kB >>>>> >>>>> >>>>> After running the test: >>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>> CmaTotal: 204800 kB >>>>> CmaFree: 6602584 kB >>>>> >>>>> So the freed CMA memory is more than total.. >>>>> >>>>> Also the the MemFree is more than mem total: >>>>> >>>>> -bash-4.3# cat /proc/meminfo >>>>> MemTotal: 16342016 kB >>>>> MemFree: 22367268 kB >>>>> MemAvailable: 22370528 kB >> [...] >>>> I played with this a bit and can see the same problem. The sanity >>>> check of CmaFree < CmaTotal generally triggers in >>>> __move_zone_freepage_state in unset_migratetype_isolate. >>>> This also seems to be present as far back as v4.0 which was the >>>> first version to have the updated accounting from Joonsoo. >>>> Were there known limitations with the new freepage accounting, >>>> Joonsoo? >>> I don't know. I also played with this and looks like there is >>> accounting problem, however, for my case, number of free page is slightly less >>> than total. I will take a look. >>> >>> Hanjun, could you tell me your malloc_size? I tested with 1 and it doesn't >>> look like your case. >> I tested with malloc_size with 2M, and it grows much bigger than 1M, also I >> did some other test: > Thanks! Now, I can re-generate erronous situation you mentioned. > >> - run with single thread with 100000 times, everything is fine. >> >> - I hack the cam_alloc() and free as below [1] to see if it's lock issue, with >> the same test with 100 multi-thread, then I got: > [1] would not be sufficient to close this race. > > Try following things [A]. And, for more accurate test, I changed code a bit more > to prevent kernel page allocation from cma area [B]. This will prevent kernel > page allocation from cma area completely so we can focus cma_alloc/release race. > > Although, this is not correct fix, it could help that we can guess > where the problem is. > > Thanks. > > [A] I tested this solution [A], it can fix the problem, as you are posting a new patch, I will test that one and leave [B] alone :) Thanks Hanjun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>