From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "thomas@monjalon.net" <thomas@monjalon.net>,
Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Joyce Kong <Joyce.Kong@arm.com>,
"konstantin.ananyev@intel.com" <konstantin.ananyev@intel.com>,
nd <nd@arm.com>,
Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2] eal/rwlock: add note about writer starvation
Date: Fri, 12 Feb 2021 00:21:19 +0000 [thread overview]
Message-ID: <DBAPR08MB5814224330DD6E75F964B6AE988B9@DBAPR08MB5814.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <6427760.fPJ3V7j96H@thomas>
<snip>
>
> 14/01/2021 17:55, Stephen Hemminger:
> > The implementation of reader/writer locks in DPDK (from first release)
> > is simple and fast. But it can lead to writer starvation issues.
> >
> > It is not easy to fix this without changing ABI and potentially
> > breaking customer applications that are expect the unfair behavior.
>
> typo: "are expect"
>
> > The wikipedia page on reader-writer problem has a similar example
> > which summarizes the problem pretty well.
>
> Maybe add the URL in the commit message?
>
> >
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > ---
> > --- a/lib/librte_eal/include/generic/rte_rwlock.h
> > +++ b/lib/librte_eal/include/generic/rte_rwlock.h
> > + * Note: This version of reader/writer locks is not fair because
^^^^^^ may be "implementation" would be better?
> > + * readers do not block for pending writers. A stream of readers can
> > + * subsequently lock out all potential writers and starve them.
> > + * This is because after the first reader locks the resource,
> > + * no writer can lock it. The writer will only be able to get the
> > + lock
> > + * when it will only be released by the last reader.
This looks good. Though the writer starvation is prominent, the reader starvation is possible if there is a stream of writers when a writer holds the lock. Should we call this out too?
>
> You did not get review, probably because nobody was Cc'ed.
> +Cc Honnappa, Joyce and Konstantin
>
next prev parent reply other threads:[~2021-02-12 0:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 19:13 [dpdk-dev] Reader-Writer lock starvation issues Stephen Hemminger
2021-01-08 21:27 ` Honnappa Nagarahalli
2021-01-11 11:52 ` Ferruh Yigit
2021-01-11 13:05 ` Honnappa Nagarahalli
2021-01-12 1:04 ` [dpdk-dev] [PATCH] eal/rwlock: add note about writer starvation Stephen Hemminger
2021-01-14 16:55 ` [dpdk-dev] [PATCH v2] " Stephen Hemminger
2021-02-11 22:51 ` Thomas Monjalon
2021-02-12 0:21 ` Honnappa Nagarahalli [this message]
2021-05-12 19:10 ` Thomas Monjalon
2021-11-08 10:18 ` Thomas Monjalon
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=DBAPR08MB5814224330DD6E75F964B6AE988B9@DBAPR08MB5814.eurprd08.prod.outlook.com \
--to=honnappa.nagarahalli@arm.com \
--cc=Joyce.Kong@arm.com \
--cc=dev@dpdk.org \
--cc=konstantin.ananyev@intel.com \
--cc=nd@arm.com \
--cc=stephen@networkplumber.org \
--cc=thomas@monjalon.net \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.