mailing list of musl libc
 help / color / mirror / code / Atom feed
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.

  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).