On 2016/3/4 14:38, Joonsoo Kim wrote: > On Fri, Mar 04, 2016 at 02:05:09PM +0800, Hanjun Guo wrote: >> On 2016/3/4 12:32, Joonsoo Kim wrote: >>> On Fri, Mar 04, 2016 at 11:02:33AM +0900, 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. >>> More correct fix is something like below. >>> Please test it. >> Hmm, this is not working: > Sad to hear that. > > Could you tell me your system's MAX_ORDER and pageblock_order? > MAX_ORDER is 11, pageblock_order is 9, thanks for your help! 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>