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From: Jason Gunthorpe <>
To: Eric Dumazet <>
Cc: Doug Ledford <>,
	linux-kernel <>,
	Eric Dumazet <>,
Subject: Re: [PATCH net] RDMA/umem: add a schedule point in ib_umem_get()
Date: Fri, 31 Jul 2020 14:17:14 -0300
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Jul 29, 2020 at 06:57:55PM -0700, Eric Dumazet wrote:
> 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.

I have seen some patches in progress to do exactly this, the
motivation is to reduce the memory consumption if a lot of pages are

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

Why [PATCH net] ?

Anyhow, applied to rdma for-next


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

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