From: Chuck Lever III <chuck.lever@oracle.com>
To: "Moritz Wanzenböck" <moritz.wanzenboeck@linbit.com>
Cc: kernel-tls-handshake <kernel-tls-handshake@lists.linux.dev>,
"open list:NETWORKING [GENERAL]" <netdev@vger.kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Subject: Re: low pending handshake limit
Date: Mon, 4 Sep 2023 15:13:25 +0000 [thread overview]
Message-ID: <90B2279F-F69B-43D2-B809-006519825D62@oracle.com> (raw)
In-Reply-To: <IIOG0S.DV0B3MDEVDQF1@linbit.com>
Hi-
> On Sep 4, 2023, at 8:39 AM, Moritz Wanzenböck <moritz.wanzenboeck@linbit.com> wrote:
>
> Hi all,
>
> I'm currently working on enabling TLS support for DRBD, so I'm very keen to use the handshake infrastructure.
I'm happy to see the handshake infrastructure get more usage.
> During testing I noticed that the allowed number of pending handshakes is quite low. This seems to stem from the following calculation:
>
> /*
> * Arbitrary limit to prevent handshakes that do not make
> * progress from clogging up the system. The cap scales up
> * with the amount of physical memory on the system.
> */
> si_meminfo(&si);
> tmp = si.totalram / (25 * si.mem_unit);
> hn->hn_pending_max = clamp(tmp, 3UL, 50UL);
>
> Which, for the typical VMs I use for testing (1Gi RAM), ends up being just 3 handshakes. The limits in general seem too low also in the best case. If a node just booted, and would start connecting to all configured DRBD devices, we could easily hit even the upper limit of 50.
>
> Also the calculation used doesn't seem to make too much sense to me. It allows more handshakes when using a smaller page size?
>
> Would it be possible to increase the number of pending handshakes?
IIRC I added the dynamic computation in response to a review
comment from Paolo (cc'd). I think the limit values are arbitrary,
we just want a sensible cap on the number of pending handshakes,
and on smaller systems, that limit should be a smaller value.
It's true that a handshake can fail if that limit is hit, but
the consumer ought to be able to retry after a brief delay in
that case.
I am open to discussing changes if retrying proves to be a
challenge.
--
Chuck Lever
next prev parent reply other threads:[~2023-09-04 15:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-04 12:39 low pending handshake limit Moritz Wanzenböck
2023-09-04 15:13 ` Chuck Lever III [this message]
2023-09-05 8:56 ` Moritz Wanzenböck
2023-09-05 11:30 ` Paolo Abeni
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=90B2279F-F69B-43D2-B809-006519825D62@oracle.com \
--to=chuck.lever@oracle.com \
--cc=kernel-tls-handshake@lists.linux.dev \
--cc=moritz.wanzenboeck@linbit.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.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.
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).