Date: Sat, 15 Jun 2024 11:04:32 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 279737] mpi3mr running out of chain in 14.1-RELEASE Message-ID: <bug-279737-227-ZmMHqBdN4g@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-279737-227@https.bugs.freebsd.org/bugzilla/> References: <bug-279737-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D279737 Muhammad Moinur Rahman <bofh@freebsd.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |Works As Intended Status|Open |Closed --- Comment #7 from Muhammad Moinur Rahman <bofh@freebsd.org> --- (In reply to Sarder Kamal from comment #6) Definitely someone can help you understand it but it's like a Pandora's Box. DMA or Direct Memory Access is used by the CPU to reduce the locking of CPU= and so that another device can independently access the Memory rather than slow= ing down the CPU. So while making these sort of requests to access the memory t= he devices uses chained request rather than sequential requests which are slow= er than hell. The problem is with the growth of the CPU markets the OS designe= rs has to keep up with the number of DMA chained request the OS can handle. FreeBSD also keeps pushing these limits to a higher value for increased performance. The more chained DMA requests you can complete that specific p= iece of hardware will be able to copy more data from the memory to the devices in each cycle without locking the CPU. Although the underlying problem is not within the driver. But now you can find some at least a bit better performa= nce with(32768) your card although I am not sure if we can benchmark it. --=20 You are receiving this mail because: You are the assignee for the bug.=
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