From: Sergey Ostanevich via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Igor Munkin <imun@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 19:59:01 +0300 [thread overview]
Message-ID: <E4C725B9-5B49-4703-8290-6A7183589F58@tarantool.org> (raw)
In-Reply-To: <20210801103633.GX27855@tarantool.org>
Hi! Thanks for the patch!
Now direct_resize() will fail if it doesn't fit into the current place
with a new size and a direct_alloc() supposedly will be called. This one
doesn't help with 47-bit address AFAIU since it has no extra option -
I doubt it exist at all - to ask kernel to fit.
So, how it helps?
Regards,
Sergos
> On 1 Aug 2021, at 13:36, Igor Munkin <imun@tarantool.org> wrote:
>
> 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 16:59 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
2021-08-01 16:59 ` Sergey Ostanevich via Tarantool-patches [this message]
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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