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From: Eric Dumazet <>
To: Doug Ledford <>, Jason Gunthorpe <>
Cc: linux-kernel <>,
	Eric Dumazet <>,
	Eric Dumazet <>,
Subject: [PATCH net] RDMA/umem: add a schedule point in ib_umem_get()
Date: Wed, 29 Jul 2020 18:57:55 -0700
Message-ID: <> (raw)

Mapping as little as 64GB can take more than 10 seconds,
triggering issues on kernels with CONFIG_PREEMPT_NONE=y.

ib_umem_get() already splits the work in 2MB units on x86_64,
adding a cond_resched() in the long-lasting loop is enough
to solve the issue.

Note that sg_alloc_table() can still use more than 100 ms,
which is also problematic. This might be addressed later
in ib_umem_add_sg_table(), adding new blocks in sgl
on demand.

Signed-off-by: Eric Dumazet <>
Cc: Doug Ledford <>
Cc: Jason Gunthorpe <>
 drivers/infiniband/core/umem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 82455a1392f1d19c96ae956f0bd4e93e3a52d29c..831bff8d52e547834e9e04064127fbb280595126 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -261,6 +261,7 @@ struct ib_umem *ib_umem_get(struct ib_device *device, unsigned long addr,
 	sg = umem->sg_head.sgl;
 	while (npages) {
+		cond_resched();
 		ret = pin_user_pages_fast(cur_base,
 					  min_t(unsigned long, npages,
 						PAGE_SIZE /

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30  1:57 Eric Dumazet [this message]
2020-07-31 17:17 ` Jason Gunthorpe
2020-07-31 17:21   ` Eric Dumazet

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