Date: Thu, 9 Apr 2020 10:28:56 -0700 From: Luigi Rizzo <rizzo@iet.unipi.it> To: =?UTF-8?B?w5Z6a2FuIEtJUklL?= <ozkan.kirik@gmail.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, freebsd-ipfw <freebsd-ipfw@freebsd.org>, "Andrey V. Elsukov" <bu7cher@yandex.ru> Subject: Re: dummynet performance Message-ID: <CA%2BhQ2%2BgDeEYFWt%2B5guFVTvsSyeL_M4KRUif6nzTpFcu=hLrVOQ@mail.gmail.com> In-Reply-To: <CAAcX-AEamLFbAucFXYJ0k3FePddYC7M-OtQRsTgQ3UWz_z%2BBBA@mail.gmail.com> References: <CAAcX-AEamLFbAucFXYJ0k3FePddYC7M-OtQRsTgQ3UWz_z%2BBBA@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Apr 9, 2020 at 2:18 AM =C3=96zkan KIRIK <ozkan.kirik@gmail.com> wro= te: > > Hello, > > I wonder if it is possible to update dummynet code multi-threading capabl= e > practically? > My idea is below: > - A new sysctl tunable will be defined as > "net.inet.ip.dummynet.thread_count" (default 1) > - To distribute tasks along threads, each sched instance can be assigned = to > different thread. > - By default, all schedulers assigned to thread 0 if no thread_id is set. > With a new option named "thr_id" affinity can be set. as below: > ipfw sched 1 config type QFQ (by defaut thr_id =3D 0) > ipfw sched 2 config type QFQ thr_id 1 > ipfw sched 3 config type QFQ thr_id 2 > ipfw sched 4 config type FIFO thr_id 3 > ipfw sched 5 config type FIFO thr_id 3 ( sched 4 & 5 assigned to same > thread 3 ) > > I think this approach is more easy then completely rewrite or other > solutions. > This change may not be completely trivial given that dummynet was designed = as single threaded and protected by a single lock. If you want to proceed, you should do as follows: - some members of struct dn_parms need to be duplicated for each thread, including prev_t, evheap, curr_time, the locks, and perhaps others. Probably may be useful to create a new struct for them, with a back pointer to the parent dn_parms, and include a refcount. - add another rwlock to protect access to dn_cfg - dummynet_io() does the initial demultiplexing calling dn_ht_find(), currently protected DN_BH_WLOCK(). This could be changed to an RWLOCK and I believe this initial step could be protected by a read lock (maybe there are corner cases where you need to create a new entry so you need to drop the lock, acquire in write mode and retry...) - once the demux has returned a dn_fsk, maybe you can use a refcount to avoid the object being destroyed, release the read lock on dn_cfg.fshash, acquire an exclusive lock on the thread handling the dn_fsk, and proceed from there. - the kernel thread that process the heap should now run each on one instance of the evheap cheers luigi
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CA%2BhQ2%2BgDeEYFWt%2B5guFVTvsSyeL_M4KRUif6nzTpFcu=hLrVOQ>