On Wed, Jul 17, 2013 at 12:50:25PM -0700, Davidlohr Bueso wrote: > From: Davidlohr Bueso <davidlohr.bu...@hp.com> > > - Cleaned up and forward ported to Linus' latest. > - Cache aligned mutexes. > - Keep non SMP systems using a single mutex. > > It was found that this mutex can become quite contended > during the early phases of large databases which make use of huge pages - for > instance > startup and initial runs. One clear example is a 1.5Gb Oracle database, where > lockstat > reports that this mutex can be one of the top 5 most contended locks in the > kernel during > the first few minutes: > > hugetlb_instantiation_mutex: 10678 10678 > --------------------------- > hugetlb_instantiation_mutex 10678 [<ffffffff8115e14e>] > hugetlb_fault+0x9e/0x340 > --------------------------- > hugetlb_instantiation_mutex 10678 [<ffffffff8115e14e>] > hugetlb_fault+0x9e/0x340 > > contentions: 10678 > acquisitions: 99476 > waittime-total: 76888911.01 us
Hello, I have a question :) So, each contention takes 7.6 ms in your result. Do you map this area with VM_NORESERVE? If we map with VM_RESERVE, when page fault, we just dequeue a huge page from a queue and clear a page and then map it to a page table. So I guess, it shouldn't take so long. I'm wondering why it takes so long. And do you use 16KB-size hugepage? If so, region handling could takes some times. If you access the area as random order, the number of region can be more than 90000. I guess, this can be one reason to too long waittime. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
