From: Szabolcs Nagy <nsz@port70.net>
To: James Y Knight <jyknight@google.com>
Cc: musl@lists.openwall.com, Florian Weimer <fweimer@redhat.com>,
Rich Felker <dalias@libc.org>, baiyang <baiyang@gmail.com>
Subject: Re: [musl] The heap memory performance (malloc/free/realloc) is significantly degraded in musl 1.2 (compared to 1.1)
Date: Tue, 20 Sep 2022 19:34:23 +0200 [thread overview]
Message-ID: <20220920173423.GE2158779@port70.net> (raw)
In-Reply-To: <CAA2zVHrZ3OfDV1upRY-DkrFw5iQBPfqVA9prB=BOyB7jKvNO8w@mail.gmail.com>
* James Y Knight <jyknight@google.com> [2022-09-20 12:59:00 -0400]:
> On Tue, Sep 20, 2022 at 9:58 AM Siddhesh Poyarekar <siddhesh@redhat.com>
> wrote:
>
> > Adding support for something that's already declared as bad
> > programming practice seems like a step backwards. Instead, I hope we
> > find a way to discourage active use of malloc_usable_size more
> > strongly.
>
>
> BTW, if folks aren't aware, there is already work on the C++ side to expose
> an API which lets you request a heap allocation of _at least_ the given
> size, which rounds the actual size up in whatever way the allocator likes,
> and returns the pointer and actual size allocated. With this API, you
> declare an explicit intent that all of the memory -- up to the returned
> size -- is valid to use without needing to go back to the allocator to ask
> for more.
>
> The proposal is still making its way through the standardization process,
> but hopefully it'll make it into the next version of C++ after C++23. (Of
> course, that's not a sure thing until it happens.) Here's the doc, with
> more rationale/etc:
> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p0901r9.html
this does not seem to discuss how existing applications
that override new() would cope with this.
nor how existing implementations on top of c allocators
would implement it (given that we just agreed that
malloc_usable_size is not suitable for such use).
nor how existing allocator tooling (interposers, profilers)
would handle the new interface.
>
> Also, as noted in the doc, jemalloc experimentally implemented this
> functionality in its non-standard API, via a function it called "smallocx"
> -- though jemalloc hides the API so it can't be used by default. The API is
> effectively:
> typedef struct { void *ptr; size_t size; } smallocx_return_t;
> smallocx_return_t smallocx(size_t size, int flags);
> https://github.com/jemalloc/jemalloc/blob/a0734fd6ee326cd2059edbe4bca7092988a63684/src/jemalloc.c#L3414
> (That's consistent with jemalloc's other non-standard APIs, which stick
> alignment/etc into a "flags" argument, but probably not suitable for a
> more-standardized cross-implementation API)
>
> tcmalloc implements similar functionality, as well, with family of
> functions named "tcmalloc_size_returning_operator_new":
so there are already incompatible c apis, which means this
should not be considered a viable proposal at this point.
>
> https://github.com/google/tcmalloc/blob/267aa2ec2817ab9d09b3fbb65ecb90193dd4348e/tcmalloc/malloc_extension.h#L549
> which of course also isn't a suitable API to support cross-implementation.
>
> If someone wants to push forward this area, IMO, it would be really great
> to have an API exposing this functionality designed to be implemented in a
> common way across libc malloc implementations -- and eventually added to
> POSIX or C.
this is done the wrong way around.
next prev parent reply other threads:[~2022-09-20 17:34 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-19 7:53 baiyang
2022-09-19 11:08 ` Szabolcs Nagy
2022-09-19 12:36 ` Florian Weimer
2022-09-19 13:46 ` Rich Felker
2022-09-19 13:53 ` James Y Knight
2022-09-19 17:40 ` baiyang
2022-09-19 18:14 ` Szabolcs Nagy
2022-09-19 18:40 ` baiyang
2022-09-19 19:07 ` Gabriel Ravier
2022-09-19 19:21 ` Rich Felker
2022-09-19 21:02 ` Gabriel Ravier
2022-09-19 21:47 ` Rich Felker
2022-09-19 22:31 ` Gabriel Ravier
2022-09-19 22:46 ` baiyang
2022-09-19 20:46 ` Nat!
2022-09-20 8:51 ` Szabolcs Nagy
2022-09-20 0:13 ` James Y Knight
2022-09-20 0:25 ` baiyang
2022-09-20 0:38 ` Rich Felker
2022-09-20 0:47 ` baiyang
2022-09-20 1:00 ` Rich Felker
2022-09-20 1:18 ` baiyang
2022-09-20 2:15 ` Rich Felker
2022-09-20 2:35 ` baiyang
2022-09-20 3:28 ` Rich Felker
2022-09-20 3:53 ` baiyang
2022-09-20 5:41 ` Rich Felker
2022-09-20 5:56 ` baiyang
2022-09-20 12:16 ` Rich Felker
2022-09-20 17:21 ` baiyang
2022-09-20 8:33 ` Florian Weimer
2022-09-20 13:54 ` Siddhesh Poyarekar
2022-09-20 16:59 ` James Y Knight
2022-09-20 17:34 ` Szabolcs Nagy [this message]
2022-09-20 19:53 ` James Y Knight
2022-09-24 8:55 ` Fangrui Song
2022-09-20 17:39 ` baiyang
2022-09-20 18:12 ` Quentin Rameau
2022-09-20 18:19 ` Rich Felker
2022-09-20 18:26 ` Alexander Monakov
2022-09-20 18:35 ` baiyang
2022-09-20 20:33 ` Gabriel Ravier
2022-09-20 20:45 ` baiyang
2022-09-21 8:42 ` NRK
2022-09-20 18:37 ` Quentin Rameau
2022-09-21 10:15 ` [musl] " 王志强
2022-09-21 16:11 ` [musl] " 王志强
2022-09-21 17:15 ` [musl] " Rich Felker
2022-09-21 17:58 ` Rich Felker
2022-09-22 3:34 ` [musl] " 王志强
2022-09-22 9:10 ` [musl] " 王志强
2022-09-22 9:39 ` [musl] " 王志强
2022-09-20 17:28 ` baiyang
2022-09-20 17:44 ` Siddhesh Poyarekar
2022-10-10 14:13 ` Florian Weimer
2022-09-19 13:43 ` Rich Felker
2022-09-19 17:32 ` baiyang
2022-09-19 18:15 ` Rich Felker
2022-09-19 18:44 ` baiyang
2022-09-19 19:18 ` Rich Felker
2022-09-19 19:45 ` baiyang
2022-09-19 20:07 ` Rich Felker
2022-09-19 20:17 ` baiyang
2022-09-19 20:28 ` Rich Felker
2022-09-19 20:38 ` baiyang
2022-09-19 22:02 ` Quentin Rameau
2022-09-19 20:17 ` Joakim Sindholt
2022-09-19 20:33 ` baiyang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220920173423.GE2158779@port70.net \
--to=nsz@port70.net \
--cc=baiyang@gmail.com \
--cc=dalias@libc.org \
--cc=fweimer@redhat.com \
--cc=jyknight@google.com \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).