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Date:   Thu, 4 Jul 2019 04:35:23 -0700 (PDT)
From:   Paul Walmsley <paul.walmsley@sifive.com>
To:     Alexandre Ghiti <alex@ghiti.fr>
cc:     Albert Ou <aou@eecs.berkeley.edu>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Will Deacon <will.deacon@arm.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Hanjun Guo <guohanjun@huawei.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-riscv@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH v3 0/2] Hugetlbfs support for riscv
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On Thu, 4 Jul 2019, Alexandre Ghiti wrote:

> On 7/4/19 12:57 AM, Paul Walmsley wrote:
> > On Mon, 1 Jul 2019, Alexandre Ghiti wrote:
> > 
> > > - libhugetlbfs testsuite on riscv64/2M:
> > >    - brk_near_huge triggers an assert in malloc.c, does not on x86.
> > I was able to reproduce the 2MB megapages test results on rv64 QEMU.  On a
> > HiFive Unleashed, though, a few more tests fail:

[ ... ]

> > - One of the heapshrink tests fails ("Heap did not shrink")
> > 
> >    # LD_PRELOAD="obj64/libhugetlbfs_privutils.so obj64/libhugetlbfs.so
> > tests/obj64/libheapshrink.so" HUGETLB_MORECORE_SHRINK=yes
> > HUGETLB_MORECORE=yes tests/obj64/heapshrink
> >    Starting testcase "tests/obj64/heapshrink", pid 753
> >    FAIL    Heap did not shrink
> >    #
> > 
> > Some of these may be related to the top-down mmap work, but there might be
> > more work to do on actual hardware.
> 
> 
> I don't think this is related to top-down mmap layout, this test only 
> mmaps a huge page. It might be interesting to see more verbose messages 
> adding HUGETLB_VERBOSE=99 when launching the test.

Here is the HUGETLB_VERBOSE=99 output from the above heapshrink test on an 
FU540:

libhugetlbfs [(none):86]: INFO: Found pagesize 2048 kB
libhugetlbfs [(none):86]: INFO: Parsed kernel version: [5] . [2] . [0]  [pre-release: 6]
libhugetlbfs [(none):86]: INFO: Feature private_reservations is present in this kernel
libhugetlbfs [(none):86]: INFO: Feature noreserve_safe is present in this kernel
libhugetlbfs [(none):86]: INFO: Feature map_hugetlb is present in this kernel
libhugetlbfs [(none):86]: INFO: Kernel has MAP_PRIVATE reservations.  Disabling heap prefaulting.
libhugetlbfs [(none):86]: INFO: Kernel supports MAP_HUGETLB
libhugetlbfs [(none):86]: INFO: HUGETLB_SHARE=0, sharing disabled
libhugetlbfs [(none):86]: INFO: HUGETLB_NO_RESERVE=no, reservations enabled
libhugetlbfs [(none):86]: INFO: No segments were appropriate for remapping
libhugetlbfs [(none):86]: INFO: setup_morecore(): heapaddr = 0x2aaac00000
libhugetlbfs [(none):86]: INFO: hugetlbfs_morecore(1052672) = ...
libhugetlbfs [(none):86]: INFO: heapbase = 0x2aaac00000, heaptop = 0x2aaac00000, mapsize = 0, delta=1052672
libhugetlbfs [(none):86]: INFO: Attempting to map 2097152 bytes
libhugetlbfs [(none):86]: INFO: ... = 0x2aaac00000
libhugetlbfs [(none):86]: INFO: hugetlbfs_morecore(0) = ...
libhugetlbfs [(none):86]: INFO: heapbase = 0x2aaac00000, heaptop = 0x2aaad01000, mapsize = 200000, delta=-1044480
libhugetlbfs [(none):86]: INFO: ... = 0x2aaad01000
Starting testcase "tests/obj64/heapshrink", pid 86
libhugetlbfs [(none):86]: INFO: hugetlbfs_morecore(33558528) = ...
libhugetlbfs [(none):86]: INFO: heapbase = 0x2aaac00000, heaptop = 0x2aaad01000, mapsize = 200000, delta=32514048
libhugetlbfs [(none):86]: INFO: Attempting to map 33554432 bytes
libhugetlbfs [(none):86]: INFO: ... = 0x2aaad01000
FAIL    Heap did not shrink


This is with this hugepage configuration:

# /usr/local/bin/hugeadm --pool-list
      Size  Minimum  Current  Maximum  Default
   2097152       64       64       64        *
#


- Paul