Date: Thu, 26 Sep 2024 22:37:43 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 281560] gve (4) uma deadlock during high tcp throughput Message-ID: <bug-281560-7501-aDVASDu0Fj@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-281560-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-281560-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D281560 --- Comment #12 from Andrew Gallatin <gallatin@FreeBSD.org> --- Comment on attachment 253834 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D253834 procstat_kka Are we absolutely certain that this is a deadlock and not a livelock? If y= ou look at network counters, etc, seconds apart do you see any movement at all= ?=20 Is that iperf killable? I'm asking this because while most of the uma locks are in the allocation p= ath, but some are in the free path (0 100421 kernel gve0 rxq 8=20= =20=20=20=20=20=20=20=20 mi_switch+0x171 __mtx_lock_sleep+0x1ba __mtx_lock_flags+0xe1 zone_put_bucket+0x75 cache_free+0x2da uma_zfree_arg+0x21c mb_free_ext+0x126 m_free+0xda m_freem+0x48 tcp_do_segment+0x1e6b tcp_input_with_port+0x1135 tcp_input+0xb ip_input+0x2ae netisr_dispatch_src+0xad ether_demux+0x17a ether_nh_input+0x3f8 netisr_dispatch_src+0xad ether_input+0xe5), and it appears that the iperf thread that holds that zone lock is actually doing something. I've seen degenerate, live-locking, behavior in the past when allocations a= nd frees overwhelm the per-cpu caches and there is contention for the zone loc= k.=20 Throughput drops by 80% or more, and the system becomes incredibly sluggish= and its easy to think it is a deadlock. --=20 You are receiving this mail because: You are the assignee for the bug.=
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