From: "Wang, Yipeng1" <yipeng1.wang@intel.com>
To: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"honnappa.nagarahalli@dpdk.org" <honnappa.nagarahalli@dpdk.org>,
"gavin.hu@arm.com" <gavin.hu@arm.com>,
"steve.capper@arm.com" <steve.capper@arm.com>,
"ola.liljedahl@arm.com" <ola.liljedahl@arm.com>,
"nd@arm.com" <nd@arm.com>,
"Gobriel, Sameh" <sameh.gobriel@intel.com>
Subject: Re: [dpdk-dev] [PATCH 0/4] Address reader-writer concurrency in rte_hash
Date: Thu, 27 Sep 2018 23:45:31 +0000 [thread overview]
Message-ID: <D2C4A16CA39F7F4E8E384D204491D7A6614D7F25@FMSMSX151.amr.corp.intel.com> (raw)
In-Reply-To: <1536253938-192391-1-git-send-email-honnappa.nagarahalli@arm.com>
Hi Honnappa,
Reply inlined:
>-----Original Message-----
>
> Currently, reader-writer concurrency problems in rte_hash are
> addressed using reader-writer locks. Use of reader-writer locks
> results in following issues:
>
> 1) In many of the use cases for the hash table, writer threads
> are running on control plane. If the writer is preempted while
> holding the lock, it will block the readers for an extended period
> resulting in packet drops. This problem seems to apply for platforms
> with transactional memory support as well because of the algorithm
> used for rte_rwlock_write_lock_tm:
>
> static inline void
> rte_rwlock_write_lock_tm(rte_rwlock_t *rwl)
> {
> if (likely(rte_try_tm(&rwl->cnt)))
> return;
> rte_rwlock_write_lock(rwl);
> }
>
> i.e. there is a posibility of using rte_rwlock_write_lock in
> failure cases.
[Wang, Yipeng] In our test, TSX failure happens very rarely on a TSX platform. But we agree
that without TSX, the current rte_rwlock implementation may make the writer to
hold a lock for a period of time.
> 2) Reader-writer lock based solution does not address the following
> issue.
> rte_hash_lookup_xxx APIs return the index of the element in
> the key store. Application(reader) can use that index to reference
> other data structures in its scope. Because of this, the
> index should not be freed till the application completes
> using the index.
[Wang, Yipeng] I agree on this use case. But I think we should provide new API functions for deletion
to users who want this behavior,
without changing the meaning of current API if that is possible.
> Current code:
> Cores Lookup Lookup
> with add
> 2 474 246
> 4 935 579
> 6 1387 1048
> 8 1766 1480
> 10 2119 1951
> 12 2546 2441
>
> With this patch:
> Cores Lookup Lookup
> with add
> 2 291 211
> 4 297 196
> 6 304 198
> 8 309 202
> 10 315 205
> 12 319 209
>
[Wang, Yipeng] It would be good if you could provide the platform information on these results.
Another comment is as you know we also have a new extension to rte_hash to enable extendable
buckets and partial-key hashing. Thanks for the comments btw. Could you check if your lockless
scheme also applies to those extensions?
next prev parent reply other threads:[~2018-09-27 23:45 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 17:12 Honnappa Nagarahalli
2018-09-06 17:12 ` [dpdk-dev] [PATCH 1/4] hash: correct key store element alignment Honnappa Nagarahalli
2018-09-27 23:58 ` Wang, Yipeng1
2018-09-06 17:12 ` [dpdk-dev] [PATCH 2/4] hash: add memory ordering to avoid race conditions Honnappa Nagarahalli
2018-09-28 0:43 ` Wang, Yipeng1
2018-09-30 22:20 ` Honnappa Nagarahalli
2018-10-01 22:41 ` Wang, Yipeng1
2018-10-01 10:42 ` Ola Liljedahl
2018-10-02 1:52 ` Wang, Yipeng1
2018-09-06 17:12 ` [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving keys Honnappa Nagarahalli
2018-09-28 1:00 ` Wang, Yipeng1
2018-09-28 8:26 ` Bruce Richardson
2018-09-28 8:55 ` Van Haaren, Harry
2018-09-30 22:33 ` Honnappa Nagarahalli
2018-10-02 13:17 ` Van Haaren, Harry
2018-10-02 23:58 ` Wang, Yipeng1
2018-10-03 17:32 ` Honnappa Nagarahalli
2018-10-03 17:56 ` Wang, Yipeng1
2018-10-03 23:05 ` Ola Liljedahl
2018-10-04 3:32 ` Honnappa Nagarahalli
2018-10-04 3:54 ` Honnappa Nagarahalli
2018-10-04 19:16 ` Wang, Yipeng1
2018-09-30 23:05 ` Honnappa Nagarahalli
2018-10-01 22:56 ` Wang, Yipeng1
2018-10-03 0:16 ` Wang, Yipeng1
2018-10-03 17:39 ` Honnappa Nagarahalli
2018-09-06 17:12 ` [dpdk-dev] [PATCH 4/4] hash: enable lock-free reader-writer concurrency Honnappa Nagarahalli
2018-09-28 1:33 ` Wang, Yipeng1
2018-10-01 4:11 ` Honnappa Nagarahalli
2018-10-01 23:54 ` Wang, Yipeng1
2018-10-11 5:24 ` Honnappa Nagarahalli
2018-09-14 21:18 ` [dpdk-dev] [PATCH 0/4] Address reader-writer concurrency in rte_hash Honnappa Nagarahalli
2018-09-26 14:36 ` Honnappa Nagarahalli
2018-09-27 23:45 ` Wang, Yipeng1 [this message]
2018-09-28 21:11 ` Honnappa Nagarahalli
2018-10-02 0:30 ` Wang, Yipeng1
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