From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: libc-alpha@sourceware.org
Subject: Re: [RFC PATCH 0/3] Improved ALSR
Date: Tue, 24 Nov 2020 11:29:56 -0300 [thread overview]
Message-ID: <9f537b66-d8d2-c0da-7b2b-3a259fb2b5e6@linaro.org> (raw)
In-Reply-To: <ea02ef0f-3aba-4be6-3565-90fb02f945b3@gmail.com>
On 24/11/2020 08:59, Topi Miettinen via Libc-alpha wrote:
> On 24.11.2020 13.24, Florian Weimer wrote:
>> * Topi Miettinen:
>>
>>> On 23.11.2020 23.45, Florian Weimer wrote:
>>>> * Topi Miettinen via Libc-alpha:
>>>>
>>>>> $ time ./malloc-vs-sbrk
>>>>>
>>>>> real 0m1.923s
>>>>> user 0m0.160s
>>>>> sys 0m1.762s
>>>>> $ time ./malloc-vs-sbrk 1
>>>>>
>>>>> real 0m2.847s
>>>>> user 0m0.176s
>>>>> sys 0m2.669s
>>>> Does the difference go away if you change the mmap granularity to
>>>> 128 KiB? I think this happens under the covers (on the kernel side)
>>>> with sbrk.
>>>
>>> Does not seem so, 56% increase:
>>
>> But the test does not seem very realistic because the pages are never
>> faulted in. Sorry, I didn't check that before.
>
> Right, this changes the equation dramatically:
>
> # time ./malloc-vs-sbrk
>
> real 0m19.498s
> user 0m1.192s
> sys 0m18.302s
> # time ./malloc-vs-sbrk 1
>
> real 0m19.428s
> user 0m1.276s
> sys 0m18.146s
>
> FYI, the effect of full ASLR of mmap() by kernel also seems small:
>
> # echo 3 >/proc/sys/kernel/randomize_va_space
> # time ./malloc-vs-sbrk
>
> real 0m19.489s
> user 0m1.263s
> sys 0m18.211s
> # time ./malloc-vs-sbrk 1
>
> real 0m19.532s
> user 0m1.148s
> sys 0m18.366s
I saw similar results showing little performance difference on different
architectures as well (aarch64, s390x, sparc64, and armhf), so I don't
think performance should an impending reason for this change.
next prev parent reply other threads:[~2020-11-24 14:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-04 13:09 Topi Miettinen
2020-10-04 13:09 ` [RFC PATCH 1/3] csu: randomize location of TCB Topi Miettinen
2020-11-24 18:44 ` Adhemerval Zanella
2020-10-04 13:09 ` [RFC PATCH 2/3] malloc: always use mmap() to improve ASLR Topi Miettinen
2020-10-04 13:09 ` [RFC PATCH 3/3] dl-sysdep: disable remaining calls to sbrk() Topi Miettinen
2020-11-23 16:06 ` [RFC PATCH 0/3] Improved ALSR Topi Miettinen
2020-11-23 16:41 ` Szabolcs Nagy
2020-11-23 17:55 ` Topi Miettinen
2020-11-23 21:45 ` Florian Weimer
2020-11-23 22:28 ` Topi Miettinen
2020-11-24 11:24 ` Florian Weimer
2020-11-24 11:59 ` Topi Miettinen
2020-11-24 14:29 ` Adhemerval Zanella [this message]
2020-11-30 10:28 ` Florian Weimer
2020-11-30 11:39 ` Topi Miettinen
2020-11-23 16:44 ` Florian Weimer
2020-11-23 18:16 ` Topi Miettinen
2020-11-24 9:47 ` Szabolcs Nagy
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