huge-pages

Currently my application periodically blocked in IO , and the output is very low . I use some command to trace the process. By using jstack i found that the app is hanging at FileOutputStream.writeBytes. By using strace -f -c -p pid to collect syscall info, i found that. For normal situation, it has both futex and write syscalls. But when it went unnormal, there are only futex syscalls. The app keeps calling futex but all failed and throw ETIMEDOUT, just like this: <futex resumed> =-1 ETIMEDOUT (Connecton timed out) futex(Ox7f823, FUTEX_WAKE_PRIVATE,1)=0 futex(Ox7f824, FUTEX_WAIT_BITSET

I'm trying to allocate a DMA buffer for a HPC workload. It requires 64GB of buffer space. In between computation, some data is offloaded to a PCIe card. Rather than copy data into a bunch of dinky 4MB buffers given by pci_alloc_consistent, I would like to just create 64 1GB buffers, backed by 1GB HugePages. Some background info: kernel version: CentOS 6.4 / 2.6.32-358.el6.x86_64 kernel boot options: hugepagesz=1g hugepages=64 default_hugepagesz=1g relevant portion of /proc/meminfo: AnonHugePages: 0 kB HugePages_Total: 64 HugePages_Free: 64 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize:

I have an application that uses hugepage and the application suddenly crashed due to some bug. After crashing, since the application does not release the hugepage properly, the free hugepage number is not increased in sys filesystem. $ sudo cat /sys/kernel/mm/hugepages/hugepages-2048kB/free_hugepages 0 $ sudo cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages 1024 Is there a way to release the hugepages by force? HugeTLB can either be used for shared memory (and Mark J. Bobak's answer would deal with that) or the app mmaps files created in a hugetlb filesystem. If the app crashes