From: "H.J. Lu" <hjl.tools@gmail.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>,
Rongwei Wang <rongwei.wang@linux.alibaba.com>,
GNU C Library <libc-alpha@sourceware.org>,
Adhemerval Zanella <adhemerval.zanella@linaro.org>,
xuyu@linux.alibaba.com, gavin.dg@linux.alibaba.com
Subject: Re: [PATCH v6 1/2] elf: Properly align PT_LOAD segments [BZ #28676]
Date: Mon, 13 Dec 2021 05:20:07 -0800 [thread overview]
Message-ID: <CAMe9rOrJjE-drb0C6v8KBxF7d4mPoPaxFxWOKn2-jAU-4g+g=g@mail.gmail.com> (raw)
In-Reply-To: <87bl1k1zrg.fsf@oldenburg.str.redhat.com>
On Mon, Dec 13, 2021 at 3:59 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Szabolcs Nagy:
>
> >> What are the p_align values of the involved objects? I would not expect
> >> any changes on 32-bit Arm because p_align and the run-time page size
> >> should match there.
> >
> > p_align is 64K
> >
> > and i see a lot of close to 64K PROT_NONE mappings
> > left behind after many dlclose which creates a lot of
> > vm fragmentation when dlopen/dlclose is called in a loop.
> >
> > (i think the mapping is at the beginning or end of
> > the lib as some kind of padding and left behind after
> > dlclose, but haven't confirmed this yet)
>
> Oh. So why there is a real bug here, I think we need to discuss what
> the change means for 64K p_align binaries on 4K kernels. Do the
> additional munmap calls matter for startup performance?
We should align munmap arguments.
> (I understand this is very much a correctness fix, but startup
> performance matters as well.)
>
The kernel loader doesn't call munmap in this case. Should
we be concerned about the unused pages?
--
H.J.
next prev parent reply other threads:[~2021-12-13 13:20 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-04 4:58 [PATCH RFC 0/1] make ld.so map .text LOAD ssegments and aligned by p_align Rongwei Wang
2021-12-04 4:58 ` [PATCH RFC 1/1] elf: align the mapping address of LOAD segments with p_align Rongwei Wang
2021-12-04 18:10 ` Florian Weimer
2021-12-06 2:47 ` Rongwei Wang
2021-12-06 14:48 ` H.J. Lu
2021-12-08 2:14 ` Rongwei Wang
2021-12-08 2:33 ` H.J. Lu
2021-12-08 3:04 ` Rongwei Wang
2021-12-08 23:52 ` H.J. Lu
2021-12-09 1:43 ` Rongwei Wang
2021-12-10 12:39 ` [PATCH v5 0/2] fix p_align on PT_LOAD segment in DSO isn't honored Rongwei Wang
2021-12-10 12:39 ` [PATCH v5 1/2] elf: Properly align PT_LOAD segments Rongwei Wang
2021-12-10 15:43 ` H.J. Lu
2021-12-10 15:45 ` Florian Weimer
2021-12-10 18:54 ` H.J. Lu
2021-12-10 18:57 ` H.J. Lu
2021-12-10 12:39 ` [PATCH v5 2/2] Add a testcase to check alignment of PT_LOAD segment Rongwei Wang
2021-12-10 13:48 ` Adhemerval Zanella
2021-12-10 15:41 ` H.J. Lu
2021-12-10 18:56 ` H.J. Lu
2021-12-10 20:05 ` Adhemerval Zanella
2021-12-10 20:24 ` H.J. Lu
2021-12-10 21:34 ` Adhemerval Zanella
2021-12-10 13:13 ` [PATCH v5 0/2] fix p_align on PT_LOAD segment in DSO isn't honored H.J. Lu
2021-12-10 13:58 ` Rongwei Wang
2021-12-13 2:51 ` [PATCH v6 " Rongwei Wang
2021-12-13 2:51 ` [PATCH v6 1/2] elf: Properly align PT_LOAD segments [BZ #28676] Rongwei Wang
2021-12-13 11:05 ` Szabolcs Nagy
2021-12-13 11:17 ` Florian Weimer
2021-12-13 11:35 ` Szabolcs Nagy
2021-12-13 11:59 ` Florian Weimer
2021-12-13 13:20 ` H.J. Lu [this message]
2021-12-13 13:26 ` Florian Weimer
2021-12-13 13:34 ` H.J. Lu
2021-12-13 11:46 ` Andreas Schwab
2021-12-13 11:52 ` Szabolcs Nagy
2021-12-13 14:51 ` Rongwei Wang
2021-12-13 17:37 ` Szabolcs Nagy
2021-12-13 17:50 ` Florian Weimer
2021-12-13 2:51 ` [PATCH v6 2/2] Add a testcase to check alignment of PT_LOAD segment Rongwei Wang
2021-12-14 2:03 ` [PATCH v6 0/2] fix p_align on PT_LOAD segment in DSO isn't honored Fangrui Song
2021-12-14 3:56 ` H.J. Lu
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