Date: Mon, 23 Aug 2010 12:51:12 -0700 From: Pyun YongHyeon <pyunyh@gmail.com> To: Andre Oppermann <andre@freebsd.org> Cc: adrian.chadd@gmail.com, freebsd-net@freebsd.org Subject: Re: 8.0-RELEASE-p3: 4k jumbo mbuf cluster exhaustion Message-ID: <20100823195112.GG1116@michelle.cdnetworks.com> In-Reply-To: <4C72CFD0.2000005@freebsd.org> References: <AANLkTikrbCFHz-CnuYcgH2JzpeH5hob0Aa2y5dwn3Hvv@mail.gmail.com> <AANLkTikYMU=wML_z=HDnkUF1PGYMVa1q-QWTrkxD%2B7EP@mail.gmail.com> <20100822222746.GC6013@michelle.cdnetworks.com> <AANLkTi=t%2BnG8isp1nf2aBec%2BFwomApNt0NBPO8LqZ%2B=9@mail.gmail.com> <4C724AD9.5020000@freebsd.org> <20100823175220.GB1116@michelle.cdnetworks.com> <4C72C622.2070302@freebsd.org> <20100823191634.GE1116@michelle.cdnetworks.com> <4C72CFD0.2000005@freebsd.org>
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On Mon, Aug 23, 2010 at 09:45:20PM +0200, Andre Oppermann wrote: > On 23.08.2010 21:16, Pyun YongHyeon wrote: > >On Mon, Aug 23, 2010 at 09:04:02PM +0200, Andre Oppermann wrote: > >>On 23.08.2010 19:52, Pyun YongHyeon wrote: > >>>On Mon, Aug 23, 2010 at 12:18:01PM +0200, Andre Oppermann wrote: > >>>>The function that is called on a socket write is sosend_generic() which > >>>>makes use of m_getm2(). This function allocates mbuf chains with the > >>>>tightest packing it can achieve. It will make use 4k (page size) mbufs > >>>>as much as it can. This is where they come from. > >>>> > >>>>It seems the 4k clusters do not get freed back to the pool after they've > >>>>been sent by the NIC and dropped from the socket buffer after the ACK > >>>>has > >>>>arrived. The leak must occur in one of these two places. The socket > >>>>buffer is unlikely as it would affect not just you but everyone else > >>>>too. > >>>>Thus the mbuf freeing after DMA/tx in the bce(4) driver is the prime > >>>>suspect. > >>>> > >>> > >>>I know bce(4) has a couple of bug in TX path(wrong dma tag, lack of > >>>bus_dmamap_sync(9) etc) but this is the same code path with/without > >>>TX checksum offloading. This is one of reason why I still do not > >>>understand what's really happening here. TX checksum offloading may > >>>introduce additional frame processing time to fill internal FIFO to > >>>compute checksum before transmitting the frame to wire such that it > >>>can change timing of TX path. This timing change might trigger the > >>>TX path bug. It's just vague guessing though. > >> > >>Had a chat with Claudio@OpenBSD and he said that the bce(4) DMA engine > >>can only access the first 1GB of physical RAM and has to use bounce > >>buffers all the time. Maybe this is related. > >> > > > >Really? I don't remember I saw such a DMA address space limitation > >in data sheet. And I don't think Broadcom made such a horrible > >thing for controllers targeted for servers. The only limitation I > >know is BCM5708 is not able to handle DMA addresses greater than > >40bits so bce(4) limits the DMA address space in DMA tag creation. > > Oops... OpenBSD bce(4) != FreeBSD bce(4). The former is for BCM440x > chips the latter for BCM57xx. > Ok, OpenBSD has bnx(4) for Broadcom NetXtreme II controllers.
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