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[2a01:cb0c:5:a600:3456:36f7:e65e:d1a0]) by smtp.gmail.com with ESMTPSA id f5sm11165286wmh.16.2020.10.09.04.55.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Oct 2020 04:55:25 -0700 (PDT) Date: Fri, 9 Oct 2020 13:55:25 +0200 From: Olivier Matz To: yang_y_yi Cc: dev@dpdk.org, jiayu.hu@intel.com, thomas@monjalon.net, yangyi01@inspur.com Message-ID: <20201009115525.GC21395@platinum> References: <2a50e80c.44f.173ac4c6d20.Coremail.yang_y_yi@163.com> <20200802202907.GJ5869@platinum> <3cf82e61.145c.173b1ed87ce.Coremail.yang_y_yi@163.com> <20200803081139.GK5869@platinum> <7584d005.5305.173b3b3389f.Coremail.yang_y_yi@163.com> <20200803123425.GM5869@platinum> <7e80eaff.148a.173b71824b0.Coremail.yang_y_yi@163.com> <76308d9c.2b0b.174ce214814.Coremail.yang_y_yi@163.com> <20201007094821.GP21395@platinum> <95e7dd5.68f2.1750cc5aee0.Coremail.yang_y_yi@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <95e7dd5.68f2.1750cc5aee0.Coremail.yang_y_yi@163.com> User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [dpdk-dev] [PATCH V1 2/3] mbuf: change free_cb interface to adapt to GSO case X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi, On Fri, Oct 09, 2020 at 05:51:23PM +0800, yang_y_yi wrote: > Olivier, thank you so much for your reply, your patch post for vhost help= me understand your concern better, I totally agree. For GSO case, let me s= how you a simple code to explain my issue. >=20 >=20 >=20 >=20 >=20 > struct rte_mbuf *pkt =3D rte_pktmbuf_alloc(mp); > virtio_dev_extbuf_alloc(pkt, data_len) > struct rte_mbuf * pkt_seg1 =3D rte_pktmbuf_alloc(indirect_pool); >=20 >=20 > rte_pktmbuf_attach(pkt_seg1, pkt); > rte_mbuf_ext_refcnt_update(pkt, -1); >=20 > struct rte_mbuf * pkt_seg2 =3D rte_pktmbuf_alloc(indirect_pool); > rte_pktmbuf_attach(pkt_seg2, pkt); > rte_mbuf_ext_refcnt_update(pkt, -1); > struct rte_mbuf *pkt_segs[2] =3D {pkt_seg1, pkt_seg2}; >=20 > rte_eth_tx_burst(dev->port_id, qid, pkt_segs, 2); >=20 >=20 > Is it a simple test you expect? The issue here is nobody explicitly calls > rte_pktmbuf_free(pkt), rte_pktmbuf_free(pkt_segX) in PMD driver won't free > "pkt", Is it clear to you now? Thank you for the small code. Yes, this is what I expected. The proper way to do this is something like this: /* create a mbuf, and attach it to an external buffer */ struct rte_mbuf *pkt =3D rte_pktmbuf_alloc(mp); virtio_dev_extbuf_alloc(pkt, data_len) /* create a new mbuf, attach it to the previous one: the resulting * mbuf is also an "external mbuf" (is has the EXT_ATTACHED_MBUF * flag, and its data is stored in the ext buffer. * See an example here: https://www.droids-corp.org/~zer0/ext-mbuf.svg */ struct rte_mbuf *pkt_seg1 =3D rte_pktmbuf_alloc(indirect_pool); rte_pktmbuf_attach(pkt_seg1, pkt); /* do the same another time */ struct rte_mbuf *pkt_seg2 =3D rte_pktmbuf_alloc(indirect_pool); rte_pktmbuf_attach(pkt_seg2, pkt); /* release the original pkt, we don't need it anymore */ rte_pktmbuf_free(pkt); /* send the new segments, they will be freed by the driver once * Tx is done. When the last packet referencing the external buffer * is freed, the free callback of the buffer will be invoked. */ struct rte_mbuf *pkt_segs[2] =3D {pkt_seg1, pkt_seg2}; rte_eth_tx_burst(dev->port_id, qid, pkt_segs, 2); Hope this is clearer now. Regards, Olivier >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 > At 2020-10-07 17:48:21, "Olivier Matz" wrote: > >Hi, > > > >On Sun, Sep 27, 2020 at 01:55:21PM +0800, yang_y_yi wrote: > >> Per GSO requirement, this is a must-have change, Jiayu, can you help r= eview > >> this series? > > > >I can't ack this patch until I have a simple and clear test case (only > >with mbuf functions, without GSO or vhost) showing the issue we have > >today with current. > > > >> Olivier, if you used the old interface, maybe you need to change your = code to > >> adapt this, I don't think we can have a better way to handle GSO case. > > > >Sorry, I don't get your point. What do I need to change in which code? > > > >(some more comments below) > > > >> At 2020-08-04 09:31:19, "yang_y_yi" wrote: > >>=20 > >> At 2020-08-03 20:34:25, "Olivier Matz" wrote: > >> >On Mon, Aug 03, 2020 at 05:42:13PM +0800, yang_y_yi wrote: > >> >> At 2020-08-03 16:11:39, "Olivier Matz" wro= te: > >> >> >On Mon, Aug 03, 2020 at 09:26:40AM +0800, yang_y_yi wrote: > >> >> >> At 2020-08-03 04:29:07, "Olivier Matz" = wrote: > >> >> >> >Hi, > >> >> >> > > >> >> >> >On Sun, Aug 02, 2020 at 07:12:36AM +0800, yang_y_yi wrote: > >> >> >> >>=20 > >> >> >> >>=20 > >> >> >> >> At 2020-07-31 23:15:43, "Olivier Matz" wrote: > >> >> >> >> >Hi, > >> >> >> >> > > >> >> >> >> >On Thu, Jul 30, 2020 at 08:08:59PM +0800, yang_y_yi@163.com = wrote: > >> >> >> >> >> From: Yi Yang > >> >> >> >> >>=20 > >> >> >> >> >> In GSO case, segmented mbufs are attached to original > >> >> >> >> >> mbuf which can't be freed when it is external. The issue > >> >> >> >> >> is free_cb doesn't know original mbuf and doesn't free > >> >> >> >> >> it when refcnt of shinfo is 0. > >> >> >> >> >>=20 > >> >> >> >> >> Original mbuf can be freed by rte_pktmbuf_free segmented > >> >> >> >> >> mbufs or by rte_pktmbuf_free original mbuf. Two kind of > >> >> >> >> >> cases should have different behaviors. free_cb won't > >> >> >> >> >> explicitly call rte_pktmbuf_free to free original mbuf > >> >> >> >> >> if it is freed by rte_pktmbuf_free original mbuf, but it > >> >> >> >> >> has to call rte_pktmbuf_free to free original mbuf if it > >> >> >> >> >> is freed by rte_pktmbuf_free segmented mbufs. > >> >> >> >> >>=20 > >> >> >> >> >> In order to fix this issue, free_cb interface has to been > >> >> >> >> >> changed, __rte_pktmbuf_free_extbuf must deliver called > >> >> >> >> >> mbuf pointer to free_cb, argument opaque can be defined > >> >> >> >> >> as a custom struct by user, it can includes original mbuf > >> >> >> >> >> pointer, user-defined free_cb can compare caller mbuf with > >> >> >> >> >> mbuf in opaque struct, free_cb should free original mbuf > >> >> >> >> >> if they are not same, this corresponds to rte_pktmbuf_free > >> >> >> >> >> segmented mbufs case, otherwise, free_cb won't free origin= al > >> >> >> >> >> mbuf because the caller explicitly called rte_pktmbuf_free > >> >> >> >> >> to free it. > >> >> >> >> >>=20 > >> >> >> >> >> Here is pseduo code to show two kind of cases. > >> >> >> >> >>=20 > >> >> >> >> >> case 1. rte_pktmbuf_free segmented mbufs > >> >> >> >> >>=20 > >> >> >> >> >> nb_tx =3D rte_gso_segment(original_mbuf, /* original mbuf = */ > >> >> >> >> >> &gso_ctx, > >> >> >> >> >> /* segmented mbuf */ > >> >> >> >> >> (struct rte_mbuf **)&gso_mbufs, > >> >> >> >> >> MAX_GSO_MBUFS); > >> >> >> >> > > >> >> >> >> >I'm sorry but it is not very clear to me what operations are= done by > >> >> >> >> >rte_gso_segment(). > >> >> >> >> > > >> >> >> >> >In the current code, I only see calls to rte_pktmbuf_attach(= ), > >> >> >> >> >which do not deal with external buffers. Am I missing someth= ing? > >> >> >> >> > > >> >> >> >> >Are you able to show the issue only with mbuf functions? It = would > >> >> >> >> >be helpful to understand what does not work. > >> >> >> >> > > >> >> >> >> > > >> >> >> >> >Thanks, > >> >> >> >> >Olivier > >> >> >> >> > > >> >> >> >> Oliver, thank you for comment, let me show you why it doesn't= work for my use case. In OVS DPDK, VM uses vhostuserclient to send large = packets whose size is about 64K because we enabled TSO & UFO, these large p= ackets use rte_mbufs allocated by DPDK virtio_net function=20 > >> >> >> >> virtio_dev_pktmbuf_alloc() (in file lib/librte_vhost/virtio_n= et.c. Please refer to [PATCH V1 3/3], I changed free_cb as below, these pac= kets use the same allocate function and the same free_cb no matter they are= TCP packet or UDP packets, in case of VXLAN TSO, most NICs can't support i= nner UDP fragment offload, so OVS DPDK has to do it by software, for UDP ca= se, the original rte_mbuf only can be freed by segmented rte_mbufs which ar= e output packets of rte_gso_segment, i.e. the original rte_mbuf only can fr= eed by free_cb, you can see, it explicitly called rte_pktmbuf_free(arg->mbu= f), the condition statement "if (caller_m !=3D arg->mbuf)" is true for this= case, this has no problem, but for TCP case, the original mbuf is delivere= d to rte_eth_tx_burst() but not segmented rte_mbufs output by rte_gso_segme= nt, PMD driver will call rte_pktmbuf_free(original_rte_mbuf) but not rte_pk= tmbuf_free(segmented_rte_mbufs), the same free_cb will be called, that mean= s original_rte_mbuf will be freed twice, you know what will happen, this is= just the issue I'm fixing. I bring in caller_m argument, it can help work = around this because caller_m is arg->mbuf and the condition statement "if (= caller_m !=3D arg->mbuf)" is false, you can't fix it without the change thi= s patch series did. > >> >> >> > > >> >> >> >I'm sill not sure to get your issue. Please, if you have a simp= le test > >> >> >> >case using only mbufs functions (without virtio, gso, ...), it = would be > >> >> >> >very helpful because we will be sure that we are talking about = the same > >> >> >> >thing. In case there is an issue, it can easily become a unit t= est. > >> >> >>=20 > >> >> >> Oliver, I think you don't get the point, free operation can't be= controlled by the application itself,=20 > >> >> >> it is done by PMD driver and triggered by rte_eth_tx_burst, I ha= ve shown pseudo code, > >> >> >> rte_gso_segment just segments a large mbuf to multiple mbufs, it= won't send them, the application > >> >> >> will call rte_eth_tx_burst to send them finally. > >> >> >> > >> >> >> > > >> >> >> >That said, I looked at vhost mbuf allocation and gso segmentati= on, and > >> >> >> >I found some strange things: > >> >> >> > > >> >> >> >1/ In virtio_dev_extbuf_alloc(), and I there are 2 paths to cre= ate the > >> >> >> > ext mbuf. > >> >> >> > > >> >> >> > a/ The first one stores the shinfo struct in the mbuf, basic= ally > >> >> >> > like this: > >> >> >> > > >> >> >> > pkt =3D rte_pktmbuf_alloc(mp); > >> >> >> > shinfo =3D rte_pktmbuf_mtod(pkt, struct rte_mbuf_ext_shared_in= fo *); > >> >> >> > buf =3D rte_malloc(NULL, buf_len, RTE_CACHE_LINE_SIZE); > >> >> >> > shinfo->free_cb =3D virtio_dev_extbuf_free; > >> >> >> > shinfo->fcb_opaque =3D buf; > >> >> >> > rte_mbuf_ext_refcnt_set(shinfo, 1); > >> >> >> > > >> >> >> > I don't think it is a good idea, because there is no guar= antee that > >> >> >> > the mbuf won't be freed before the buffer. For instance, = doing > >> >> >> > this will probably fail: > >> >> >> > > >> >> >> > pkt2 =3D rte_pktmbuf_alloc(mp); > >> >> >> > rte_pktmbuf_attach(pkt2, pkt); > >> >> >> > rte_pktmbuf_free(pkt); /* pkt is freed, but it contains shinf= o ! */ > >> >> >>=20 > >> >> >> pkt is created by the application I can control, so I can contro= l it where it will be freed, right? > >> >> > > >> >> >This example shows that mbufs allocated like this by the vhost > >> >> >driver are not constructed correctly. If an application attach a n= ew > >> >> >packet (pkt2) to it and frees the original one (pkt), it may resul= t in a > >> >> >memory corruption. > >> >> > > >> >> >Of course, to be tested and confirmed. > >> >>=20 > >> >> No, attach will increase refcnt of shinfo, free_cb only is called w= hen refcnt of shinfo is decreased to > >> >> 0, isn't it? > >> > > >> >When pkt will be freed, it will decrement the shinfo refcnt, and > >> >after it will be 1. So the buffer won't be freed. After that, the > >> >mbuf pkt will be detached, and will return to the mbuf pool. It means > >> >it can be reallocated, and the next user can overwrite shinfo which > >> >is still stored in the mbuf data. > >>=20 > >> I think this is an issue of DPDK itself, if external buffer in shinfo = is freed, shinfo should be set to NULL, if user will > >> overwrite it, he/she should use the same way as a new external buffer = is attached.=20 > > > >No, there is no issue in DPDK. The lifetime of shinfo should be at least > >the same the lifetime of the buffer. If shinfo is stored in initial mbuf > >(called "pkt" in the example above), the mbuf and shinfo can be freed wh= ile > >the buffer is still in use by another packet. > > > >> >I did a test to show it, see: > >> >http://git.droids-corp.org/?p=3Ddpdk.git;a=3Dcommitdiff;h=3Da617494ee= b01ff > >> > > >> >If you run the mbuf autotest, it segfaults. > >>=20 > >> I think your test is wrong, you're changing shinfo (which is being use= d) in wrong way, if free_bc is NULL, it will be invalid. > > > >I'm changing the data of a newly allocated mbuf, it is perfectly legal. > >I happens that it points the the shinfo that is still in use. > > > > > >>=20 > >> static inline void > >> rte_pktmbuf_attach_extbuf(struct rte_mbuf *m, void *buf_addr, > >> rte_iova_t buf_iova, uint16_t buf_len, > >> struct rte_mbuf_ext_shared_info *shinfo) > >> { > >> /* mbuf should not be read-only */ > >> RTE_ASSERT(RTE_MBUF_DIRECT(m) && rte_mbuf_refcnt_read(m) =3D= =3D 1); > >> RTE_ASSERT(shinfo->free_cb !=3D NULL); > >>=20 > >> For any shinfo operation, you should do it by rte_pktmbuf_attach_extbu= f, you can't change it at will after that. > >>=20 > >> > > >> > > >> >>=20 > >> >> > > >> >> >>=20 > >> >> >> > > >> >> >> > To do this properly, the mbuf refcnt should be increased,= and > >> >> >> > the mbuf should be freed in the callback. But I don't thi= nk it's > >> >> >> > worth doing it, given the second path (b/) looks good to = me. > >> >> >> > > >> >> >> > b/ The second path stores the shinfo struct at the end of the > >> >> >> > allocated buffer, like this: > >> >> >> > > >> >> >> > pkt =3D rte_pktmbuf_alloc(mp); > >> >> >> > buf_len +=3D sizeof(*shinfo) + sizeof(uintptr_t); > >> >> >> > buf_len =3D RTE_ALIGN_CEIL(total_len, sizeof(uintptr_t)); > >> >> >> > buf =3D rte_malloc(NULL, buf_len, RTE_CACHE_LINE_SIZE); > >> >> >> > shinfo =3D rte_pktmbuf_ext_shinfo_init_helper(buf, &buf_len, > >> >> >> > virtio_dev_extbuf_free, buf); > >> >> >> > > >> >> >> > I think this is correct, because we have the guarantee th= at shinfo > >> >> >> > exists as long as the buffer exists. > >> >> >>=20 > >> >> >> What buffer does the allocated buffer you're saying here? The is= sue we're discussing how we can > >> >> >> free original mbuf which owns shinfo buffer. > >> >> > > >> >> >I don't get your question. > >> >> > > >> >> >I'm just saying that this code path looks correct, compared to > >> >> >the previous one. > >> >>=20 > >> >> I think you're challenging principle of external mbuf, that isn't t= he thing I address. > >> > > >> >I'm not challenging anything, I'm saying there is a bug in this code, > >> >and the unit test above tends to confirm it. > >>=20 > >> If it is bug, you can post a patch to fix it, it isn't related with m= y patches. But in my opinion, you don't > >> use it in correct way, I don't think it is a bug. > > > >I'll submit a patch for this. > > > >The point is you are testing GSO on top of wrongly-constructed mbufs, so > >it would be safer for you to fix this before doing more tests. > > > > > >> >> >> >2/ in rte_gso_segment(), there is a loop like this: > >> >> >> > > >> >> >> > while (pkt_seg) { > >> >> >> > rte_mbuf_refcnt_update(pkt_seg, -1); > >> >> >> > pkt_seg =3D pkt_seg->next; > >> >> >> > } > >> >> >> > > >> >> >> > You change it to take in account the refcnt for ext mbufs. > >> >> >> > > >> >> >> > I may have missed something but I wonder why it is not simpl= y: > >> >> >> > > >> >> >> > rte_pktmbuf_free(pkt_seg); > >> >> >> > > >> >> >> > It will decrease the proper refcnt, and free the mbufs if th= ey > >> >> >> > are not used. > >> >> >>=20 > >> >> >> Again, rte_gso_segment just decreases refcnt by one, this will e= nsure the last segmented=20 > >> >> >> mbuf free will trigger freeing original mbuf (only free_cb can d= o this). > >> >> > > >> >> >rte_pktmbuf_free() will also decerase the refcnt, and free the res= ources > >> >> >when the refcnt reaches 0. > >> >> > > >> >> >It has some advantages compared to decrease the reference counter = of all > >> >> >segments: > >> >> > > >> >> >- no need to iterate the segments, there is only one function call > >> >> >- no need to have a special case for ext mbufs like you did in you= r patch > >> >> >- it may be safer, in case some segments have a refcnt =3D=3D 1, b= ecause > >> >> > resources will be freed. > >> >>=20 > >> >> For external mbuf, attach only increases refcnt of shinfo, refcnt o= f mbuf won't be touched. For normal > >> >> mbuf, attach only increase refcnt of mbuf, no shinfo there, no refc= nt of shinfo increased. > >> > > >> >I suppose rte_gso_segment() can take any mbuf type as input: standard > >> >mbuf, indirect mbuf, ext mbuf, or even a mbuf chaing containing segme= nts of > >> >different types. > >> > > >> >For instance, if you pass a chain of 2 mbufs: > >> >- the first one is a direct mbuf containing the IP/TCP headers (orig_= hdr) > >> >- the second on is a mbuf pointing to an ext buffer (orig_payload) > >> > > >> >I expect that the resulting mbuf after calling gso contains a list of= mbufs > >> >like this: > >> >- a first segment containing the IP/TCP headers (new_hdr) > >> >- a payload segment pointing on the same ext buffer > >> > > >> >In theory, there is no reason that orig_hdr should be referenced by > >> >another new mbuf, because it only contains headers (no data). If that= 's > >> >the case, its refcnt is 1, and decreasing it to 0 without freeing it > >> >is a bug. > >>=20 > >> For this user scenario, orig_m is owner of external buffer, small segm= ented mbufs reference > >> it, you shouldn't free orig_m before all attached segmented mbufs are = freed, isn't it? > > > >In this case, orig_hdr has to be freed because it is a direct mbuf (not > >shared). > >The buffer pointed by orig_payload will be freed when all newly created > >segments are freed. > > > > > >> > > >> >Anyway, there is maybe no issue in that case, but I was just suggesti= ng > >> >that using rte_pktmbuf_free() is easier to read, and safer than manua= lly > >> >decreasing the refcnt of each segment. > >> > > >> > > >> >> >> >Again, sorry if this is not the issue your are referring to, but > >> >> >> >in this case I really think that having a simple example code t= hat > >> >> >> >shows the issue would help. > >> >> >>=20 > >> >> >> Oliver, my statement in the patch I sent out has pseudo code to = show this. I don't think a simple > >> >> >> unit test can show it. > >> >> > > >> >> >I don't see why. The PMDs and the libraries use the mbuf functions= , why > >> >> >a unit test couldn't call the same functions? > >> >> > > >> >> >> Let me summarize it here again. For original mbuf, there are two= cases freeing > >> >> >> it, case one is PMD driver calls free against segmented mbufs, l= ast segmented mbuf free will trigger > >> >> >> free_cb call which will free original large & extended mbuf. > >> >> > > >> >> >OK > >> >> > > >> >> >> Case two is PMD driver will call free against > >> >> >> original mbuf, that also will call free_cb to free attached exte= nded buffer. > >> >> > > >> >> >OK > >> >> > > >> >> >And what makes that case 1 or case 2 is executed? > >> >> > > >> >> >> In case one free_cb must call > >> >> >> rte_pktmbuf_free otherwise nobody will free original large & ext= ended mbuf, in case two free_cb can't=20 > >> >> >> call rte_pktmbuf_free because the caller calling it is just rte_= pktmbuf_free we need. That is to say, you > >> >> >> must use the same free_cb to handle these two cases, this is my = issue and the point you don't get. > >> >> > > >> >> >I think there is no need to change the free_cb API. It should work= like > >> >> >this: > >> >> > > >> >> >- virtio creates the original external mbuf (orig_m) > >> >> >- gso will create a new mbuf referencing the external buffer (new_= m) > >> >> > > >> >> >At this point, the shinfo has a refcnt of 2. The large buffer will= be > >> >> >freed as soon as rte_pktmbuf_free() is called on orig_m and new_m, > >> >> >whatever the order. > >> >> > > >> >> >Regards, > >> >> >Olivier > >> >>=20 > >> >> Oliver, the reason it works is I changed free_cb API, case 1 doesn'= t know orig_m, how you make it free orig_m in free_cb. > >> >> The intention I change free_cb is to let it know orig_m, I saw OVS = DPDK ran out out buffers and orig_m isn't freed, that is why > >> >> I want to bring in this to fix the issue. Again, in case 1, nobody = explicitly calls ret_pktmbuf_free(orig_m) except free_cb I changed. > >> > > >> >If nobody calls ret_pktmbuf_free(orig_m), it is a problem. > >> >The free_cb is to free the buffer, not the mbuf. > >> > > >> >To me, it should work like this: > >> > > >> >1- virtio creates a mbuf attached to the ext buffer (the shinfo place= ment > >> > bug should be fixed) > >> >2- gso create mbufs that reference the the same ext buf (by attaching= the > >> > new mbuf) > >> >3- gso must free the original mbuf > >>=20 > >> This is impossible, segmented mbufs are referencing external buffer in= original mbuf, > >> how do you free it? As I said rte_gso_segment has no way to free it, p= lease tell me a way if > >> you know how to do this. > > > >As I said above, calling rte_mbuf_free(orig_m) will decrement the refere= nce > >counters on all segments. The segments will be returned to the pool if t= he > >refcnt reaches 0. > > > >>=20 > >> >4- the PMD transmits the new mbufs, and frees them > >> > > >> >Whatever 3- or 4- is executed first, at the end we are sure that: > >> >- all mbufs will be returned to the pool > >> >- the linear buffer will be freed when the refcnt reaches 0. > >> > > >> >If this is still unclear, please, write a unit test like I did > >> >above to show your issue. > >> > > >> >Regards, > >> >Olivier > >> > > >>=20 > >> The issue is in "3- gso must free the original mbuf", rte_pktmbuf_free= (segmented_mbus) can't do it, > >> rte_gso_segment is impossible to do it, only feasible point is free_cb= , please let me know if you have > >> a better way to free original mbuf and don't impact on segmented mbufs= in PMD. My point is you must > >> have a place to call rte_pktmbuf_free(rogin_m) explicitly, otherwise i= t is impossible to return it to memory > >> pool, please point out where it can be called in my user scenario. I = don't care how it is done, I just care it can > >> fix my issue, please don't hesitate and send me a patch if you can, th= anks a lot. > > > >Sorry, but I don't see how I can be clearer to what I explained > >in my previous answer. > > > >Please, *provide a simple test example* without gso/vhost, and I can help > >to make it work. > > > > > >Regards, > >Olivier > > > > > >> > > >> > > >> >> free_cb must handle case 1 and case 2 in the same code, for case 1,= caller_m is segmented new_m, for case 2, caller_m is orig_m. > >> >>=20 > >> >> loop in rte_gso_segement is handling original mbuf (this mbuf is mu= lti-mbuf and includes multiple mbufs which are linked by next > >> >> pointer), it isn't a problem at all. > >> >>=20 > >> >> Please show me code how you can fix my issue if you don't change fr= ee_cb, thank you. > >> >>=20 > >> >> struct shinfo_arg { > >> >> void *buf; > >> >> struct rte_mbuf *mbuf; > >> >> }; > >> >>=20 > >> >> virtio_dev_extbuf_free(struct rte_mbuf *caller_m, void *opaque) > >> >> { > >> >> struct shinfo_arg *arg =3D (struct shinfo_arg *)opaque; > >> >>=20 > >> >> rte_free(arg->buf); > >> >> if (caller_m !=3D arg->mbuf) > >> >> rte_pktmbuf_free(arg->mbuf); > >> >> rte_free(arg); > >> >> }