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NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | RETURN VALUE | SEE ALSO | AUTHOR | COLOPHON |
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IBV_ADVISE_MR(3) Libibverbs Programmer’s Manual IBV_ADVISE_MR(3)
ibv_advise_mr - Gives advice or directions to the kernel about an
address range belongs to a memory region (MR).
#include <infiniband/verbs.h>
int ibv_advise_mr(struct ibv_pd *pd,
enum ibv_advise_mr_advice advice,
uint32_t flags,
struct ibv_sge *sg_list,
uint32_t num_sge)
ibv_advise_mr() Give advice or directions to the kernel about an
address range belonging to a memory region (MR). Applications
that are aware of future access patterns can use this verb in
order to leverage this knowledge to improve system or application
performance.
Conventional advice values
IBV_ADVISE_MR_ADVICE_PREFETCH
Pre-fetch a range of an on-demand paging MR. Make pages
present with read-only permission before the actual IO is
conducted. This would provide a way to reduce latency by
overlapping paging-in and either compute time or IO to
other ranges.
IBV_ADVISE_MR_ADVICE_PREFETCH_WRITE
Like IBV_ADVISE_MR_ADVICE_PREFETCH but with read-access and
write-access permission to the fetched memory.
IBV_ADVISE_MR_ADVICE_PREFETCH_NO_FAULT
Pre-fetch a range of an on-demand paging MR without
faulting. This allows presented pages in the CPU to become
presented to the device.
pd The protection domain (PD) associated with the MR.
advice The requested advise value (as listed above).
flags Describes the properties of the advise operation
Conventional advice values IBV_ADVISE_MR_FLAG_FLUSH :
Request to be a synchronized operation. Return to the
caller after the operation is completed.
sg_list
Pointer to the s/g array When using IBV_ADVISE_OP_PREFETCH
advise value, all the lkeys of all the scatter gather
elements (SGEs) must be associated with ODP MRs (MRs that
were registered with IBV_ACCESS_ON_DEMAND).
num_sge
Number of elements in the s/g array
ibv_advise_mr() returns 0 when the call was successful, or the
value of errno on failure (which indicates the failure reason).
EOPNOTSUPP
libibverbs or provider driver doesn’t support the
ibv_advise_mr() verb (ENOSYS may sometimes be returned by
old versions of libibverbs).
ENOTSUP
The advise operation isn’t supported.
EFAULT In one of the following: o When the range requested is out
of the MR bounds, or when parts of it are not part of the
process address space. o One of the lkeys provided in the
scatter gather list is invalid or with wrong write access.
EINVAL In one of the following: o The PD is invalid. o The flags
are invalid. o The requested address doesn’t belong to a
MR, but a MW or something.
EPERM In one of the following: o Referencing a valid lkey outside
the caller’s security scope. o The advice is
IBV_ADVISE_MR_ADVICE_PREFETCH_WRITE but the specified MR in
the scatter gather list is not registered as writable
access.
ENOENT The providing lkeys aren’t consistent with the MR’s.
ENOMEM Not enough memory. # NOTES
An application may pre-fetch any address range within an ODP MR
when using the IBV_ADVISE_MR_ADVICE_PREFETCH or
IBV_ADVISE_MR_ADVICE_PREFETCH_WRITE advice. Semantically, this
operation is best-effort. That means the kernel does not
guarantee that underlying pages are updated in the HCA or the
pre-fetched pages would remain resident.
When using IBV_ADVISE_MR_ADVICE_PREFETCH or
IBV_ADVISE_MR_ADVICE_PREFETCH_WRITE advice, the operation will be
done in the following stages: o Page in the user pages to memory
(pages aren’t pinned). o Get the dma mapping of these user pages.
o Post the underlying page translations to the HCA.
If IBV_ADVISE_MR_FLAG_FLUSH is specified then the underlying pages
are guaranteed to be updated in the HCA before returning SUCCESS.
Otherwise the driver can choose to postpone the posting of the new
translations to the HCA. When performing a local RDMA access
operation it is recommended to use IBV_ADVISE_MR_FLAG_FLUSH flag
with one of the pre-fetch advices to increase probability that the
pages translations are valid in the HCA and avoid future page
faults.
ibv_reg_mr(3), ibv_rereg_mr(3), ibv_dereg_mr(3)
Aviad Yehezkel ⟨aviadye@mellanox.com⟩
This page is part of the rdma-core (RDMA Core Userspace Libraries
and Daemons) project. Information about the project can be found
at ⟨https://github.com/linux-rdma/rdma-core⟩. If you have a bug
report for this manual page, send it to
linux-rdma@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-04.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
libibverbs 2018-10-19 IBV_ADVISE_MR(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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