From: Cong Wang <xiyou.wangcong@gmail.com>
To: Vlad Buslov <vladbu@mellanox.com>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>, David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] net: sched: don't release block->lock when dumping chains
Date: Wed, 27 Feb 2019 15:03:20 -0800 [thread overview]
Message-ID: <CAM_iQpXbqfWOx+q3ZKfdwExnUtPgu5Qj5PU_itBND8hj-ud7DQ@mail.gmail.com> (raw)
In-Reply-To: <vbf36oamsz3.fsf@mellanox.com>
On Tue, Feb 26, 2019 at 8:10 AM Vlad Buslov <vladbu@mellanox.com> wrote:
>
>
> On Tue 26 Feb 2019 at 00:15, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > On Mon, Feb 25, 2019 at 7:45 AM Vlad Buslov <vladbu@mellanox.com> wrote:
> >>
> >> Function tc_dump_chain() obtains and releases block->lock on each iteration
> >> of its inner loop that dumps all chains on block. Outputting chain template
> >> info is fast operation so locking/unlocking mutex multiple times is an
> >> overhead when lock is highly contested. Modify tc_dump_chain() to only
> >> obtain block->lock once and dump all chains without releasing it.
> >>
> >> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
> >> Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
> >
> > Thanks for the followup!
> >
> > Isn't it similar for __tcf_get_next_proto() in tcf_chain_dump()?
> > And for tc_dump_tfilter()?
>
> Not really. These two dump all tp filters and not just a template, which
> is O(n) on number of filters and can be slow because it calls hw offload
> API for each of them. Our typical use-case involves periodic filter dump
> (to update stats) while multiple concurrent user-space threads are
> updating filters, so it is important for them to be able to execute in
> parallel.
Hmm, but if these are read-only, you probably don't even need a
mutex, you can just use RCU read lock to protect list iteration
and you still can grab the refcnt in the same way.
next prev parent reply other threads:[~2019-02-27 23:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-25 15:45 [PATCH net-next] net: sched: don't release block->lock when dumping chains Vlad Buslov
2019-02-25 18:25 ` David Miller
2019-02-26 0:15 ` Cong Wang
2019-02-26 16:09 ` Vlad Buslov
2019-02-27 23:03 ` Cong Wang [this message]
2019-02-28 14:53 ` Vlad Buslov
2019-03-02 0:08 ` Cong Wang
2019-03-04 14:14 ` Vlad Buslov
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=CAM_iQpXbqfWOx+q3ZKfdwExnUtPgu5Qj5PU_itBND8hj-ud7DQ@mail.gmail.com \
--to=xiyou.wangcong@gmail.com \
--cc=davem@davemloft.net \
--cc=jhs@mojatatu.com \
--cc=jiri@resnulli.us \
--cc=netdev@vger.kernel.org \
--cc=vladbu@mellanox.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).