From: Igor Munkin via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Sergey Kaplun <skaplun@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: Re: [Tarantool-patches] [PATCH luajit 2/2] Linux/ARM64: Make mremap() non-moving due to VA space woes. Date: Sun, 1 Aug 2021 13:36:33 +0300 [thread overview] Message-ID: <20210801103633.GX27855@tarantool.org> (raw) In-Reply-To: <YQFNso1z3FAbd/5L@root> Sergey, Thanks for the fixes! LGTM, except the single typo. On 28.07.21, Sergey Kaplun wrote: <snipped> > > The new commit message is the following: > > =================================================================== > Linux/ARM64: Make mremap() non-moving due to VA space woes. > > This reduces overall performance on ARM64, but we have no choice. > Linux kernel default userspace VA is 48 bit, but we'd need 47 bit. > mremap() ignores address hints due to a kernel API issue. The mapping > may move to an undesired address which will cause an assert or crash. > > Reported by Raymond W. Ko. > > (cherry picked from commit 67dbec82f4f05a416a78a560a726553beaa7a223) > > 47-bit VA space is required by LuaJIT for keeping a GC object pointer in > TValue. In case of huge blobs that are mapped directly, `mremap()` may > move the chunk out of 47-bit range of VA space on ARM64. `mremap()` > accepts the fifth argument (new address hint) only with MREMAP_FIXED > flag. In that case it unmaps any other mapping to specified address. > > To avoid this behaviour this patch restricts `mremap()` to relocate > the mapping to a new virtual address by set CALL_MREMAP_NOMOVE flag Typo: s/set/setting/. > instead of CALL_MREMAP_MAYMOVE for arm64 architecture. > > Sergey Kaplun: > * added the description and the test for the problem > > Needed for tarantool/tarantool#6154 Minor: Why #5629 is not mentioned? > =================================================================== > <snipped> > > -- > Best regards, > Sergey Kaplun -- Best regards, IM
next prev parent reply other threads:[~2021-08-01 11:00 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-06 17:40 [Tarantool-patches] [PATCH luajit 0/2] arm64: fix 48-bit addresses issues Sergey Kaplun via Tarantool-patches 2021-07-06 17:40 ` [Tarantool-patches] [PATCH luajit 1/2] Add support for full-range 64 bit lightuserdata Sergey Kaplun via Tarantool-patches 2021-07-27 13:59 ` Igor Munkin via Tarantool-patches 2021-07-28 12:29 ` Sergey Kaplun via Tarantool-patches 2021-08-01 10:36 ` Igor Munkin via Tarantool-patches 2021-08-02 14:56 ` Sergey Kaplun via Tarantool-patches 2021-08-01 16:25 ` Sergey Ostanevich via Tarantool-patches 2021-08-02 14:51 ` Sergey Kaplun via Tarantool-patches 2021-08-02 15:42 ` Igor Munkin via Tarantool-patches 2021-08-10 16:46 ` Sergey Ostanevich via Tarantool-patches 2021-08-11 5:54 ` Vitaliia Ioffe via Tarantool-patches 2021-07-06 17:40 ` [Tarantool-patches] [PATCH luajit 2/2] Linux/ARM64: Make mremap() non-moving due to VA space woes Sergey Kaplun via Tarantool-patches 2021-07-27 15:23 ` Igor Munkin via Tarantool-patches 2021-07-28 12:29 ` Sergey Kaplun via Tarantool-patches 2021-08-01 10:36 ` Igor Munkin via Tarantool-patches [this message] 2021-08-01 16:59 ` Sergey Ostanevich via Tarantool-patches 2021-08-02 15:08 ` Sergey Kaplun via Tarantool-patches 2021-08-02 15:55 ` Sergey Ostanevich via Tarantool-patches 2021-08-02 15:11 ` Sergey Kaplun via Tarantool-patches 2021-08-11 7:21 ` [Tarantool-patches] [PATCH luajit 0/2] arm64: fix 48-bit addresses issues Igor Munkin via Tarantool-patches
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