From: Phil Sutter <phil@nwl.cc>
To: David Ahern <dsahern@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>,
Hangbin Liu <liuhangbin@gmail.com>,
netdev@vger.kernel.org, Michal Kubecek <mkubecek@suse.cz>
Subject: Re: [PATCHv5 iproute2 net-next 2/2] lib/libnetlink: re malloc buff if size is not enough
Date: Thu, 26 Oct 2017 17:33:40 +0200 [thread overview]
Message-ID: <20171026153340.GX32305@orbyte.nwl.cc> (raw)
In-Reply-To: <25f0ec07-e36a-510c-c01f-56df8a843f80@gmail.com>
On Thu, Oct 26, 2017 at 09:28:00AM -0600, David Ahern wrote:
> On 10/26/17 4:24 AM, Stephen Hemminger wrote:
> >>
> >> The kernel needs a flag that says "give me the message of the buffer is
> >> large enough; if not just PEEK and tell me the length." That would avoid
> >> the double call in most cases.
> >
> > Actually this has little impact because old code was doing implicit zero
> > of whole buffer, new code does not.
> >
>
> The patch calls recvmsg twice; libnl does the same thing. It would be
> better performance wise to have a flag that allows retrieval of the
> message if the supplied buffer is large enough and PEEK semantics if
> not. It was really a comment on how we could do better with proper
> kernel support.
Doesn't MSG_TRUNC without MSG_PEEK do just that?
Cheers, Phil
next prev parent reply other threads:[~2017-10-26 15:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-26 1:41 [PATCHv5 iproute2 net-next 0/2] libnetlink: malloc correct buff at run time Hangbin Liu
2017-10-26 1:41 ` [PATCHv5 iproute2 net-next 2/2] lib/libnetlink: re malloc buff if size is not enough Hangbin Liu
2017-10-26 2:59 ` David Ahern
2017-10-26 10:24 ` Stephen Hemminger
2017-10-26 15:28 ` David Ahern
2017-10-26 15:33 ` Phil Sutter [this message]
2017-10-26 15:42 ` David Ahern
2017-10-26 18:31 ` Phil Sutter
2019-02-12 23:32 ` Eric Dumazet
2019-02-12 23:43 ` Eric Dumazet
2017-10-26 1:41 ` [PATCHv5 iproute2 net-next 2/2] lib/libnetlink: update rtnl_talk to support malloc buff at run time Hangbin Liu
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