UCT/IB: Skip madvise with DONT_FORK if kernel supports RDMA copy-on-fork#11573
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tvegas1 wants to merge 4 commits into
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UCT/IB: Skip madvise with DONT_FORK if kernel supports RDMA copy-on-fork#11573tvegas1 wants to merge 4 commits into
tvegas1 wants to merge 4 commits into
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tvegas1
commented
Jun 24, 2026
| static int uct_ib_fork_init_is_unneeded() | ||
| { | ||
| #if HAVE_DECL_IBV_IS_FORK_INITIALIZED && HAVE_DECL_IBV_FORK_UNNEEDED | ||
| if (ibv_is_fork_initialized() == IBV_FORK_UNNEEDED) { |
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guy-ealey-morag
previously approved these changes
Jun 24, 2026
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/azp run UCX PR |
|
Azure Pipelines successfully started running 1 pipeline(s). |
tomerg-nvidia
previously approved these changes
Jun 25, 2026
brminich
reviewed
Jun 25, 2026
| } | ||
| } | ||
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| static int uct_ib_is_fork_init_unneeded() |
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maybe uct_ib_is_fork_unneeded()
i'd even call it uct_ib_is_fork_needed() but it will not be consistent with verbs
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@tvegas1: uct_ib_fork_init_is_unneeded
@guy-ealey-morag request: uct_ib_is_fork_init_unneeded
@brminich request: uct_ib_is_fork_unneeded / uct_ib_is_fork_needed
are we all ok with uct_ib_is_fork_init_needed? i think it is ibv_fork_init call that is either needed or not.
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guy-ealey-morag
approved these changes
Jun 26, 2026
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What
Detect
IBV_FORK_UNNEEDEDin the IB fork-init path and skip UCX-side fork initialization handling in that case.Why
When the kernel supports RDMA copy-on-fork, libibverbs does not need
MADV_DONTFORKtracking. That old path can split VMAs on every registration and hitvm.max_map_count, causingmadvise()to fail withENOMEMeven when physical memory is available.How
Add configure checks for
IBV_FORK_UNNEEDEDandibv_is_fork_initialized(). Inuct_ib_fork_init(), return success withfork_initunset when libibverbs reports fork handling is unneeded.