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MPTs
Commit f4ec9e9 "mlx4_core: Change bitmap allocator to work in round-robin fashion"
introduced round-robin allocation (via bitmap) for all resources which allocate
via a bitmap.
Round robin allocation is desirable for mcgs, counters, pd's, UARs, and xrcds.
These are simply numbers, with no involvement of ICM memory mapping.
Round robin is required for QPs, since we had a problem with immediate
reuse of a 24-bit QP number (commit f4ec9e9).
However, for other resources which use the bitmap allocator and involve
mapping ICM memory -- MPTs, CQs, SRQs -- round-robin is not desirable.
What happens in these cases is the following:
ICM memory is allocated and mapped in chunks of 256K.
Since the resource allocation index goes up monotonically, the allocator
will eventually require mapping a new chunk. Now, chunks are also unmapped
when their reference count goes back to zero. Thus, if a single app is
running and starts/exits frequently we will have the following situation:
When the app starts, a new chunk must be allocated and mapped.
When the app exits, the chunk reference count goes back to zero, and the
chunk is unmapped and freed. Therefore, the app must pay the cost of allocation
and mapping of ICM memory each time it runs (although the price is paid only when
allocating the initial entry in the new chunk).
For apps which allocate MPTs/SRQs/CQs and which operate as described above,
this presented a performance problem.
We therefore roll back the round-robin allocator modification for MPTs, CQs, SRQs.
Reported-by: Matthew Finlay <matt@mellanox.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Under most circumstances, the bitmap allocator does not allocate the
same full 24-bit QP number immediately after a QP is destroyed.
This works by using the upper bits of a 24-bit QP number, beyond the
number of QPs that are actually available in the low level driver.
For example, say that the HCA is willing to allocate a maximum of 64K
qps. We use the bits 23..16 as a "counter" which is incremented by 1
at each allocation so that even if the same physical QP is
re-allocated, it will not receive the same 24-bit QP number.
However, we have seen the following scenario:
1. Allocate, say, 255 QPs in succession. This will cause a wrap of the "counter".
2. Destroy the first QP allocated, then allocate a new QP. The new QP,
because of the counter wraparound, will get the same FULL QP number as
the QP just destroyed!
This is a problem because packets in transit can be erroneously
delivered to the new QP when they were meant for the old (destroyed)
QP, because the full QP number of the new QP is identical to the
destroyed QP. (The "counter" mechanism is meant to prevent this by
having the full 24-bit QP numbers differ even if the physical QP on
the HCA is the same. As we see above, however, this mechanism does
not always work).
The best fix for this problem is to allocate QPs in round-robin mode,
so that the physical QP numbers are not immediately re-used.
Found-by: Matthew Finlay <matt@mellanox.com>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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These were getting the macros from an implicit module.h
include via device.h, but we are planning to clean that up.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
drivers/net: Add export.h to wireless/brcm80211/brcmfmac/bcmsdh.c
This relatively recently added file uses EXPORT_SYMBOL and hence
needs export.h included so that it is compatible with the module.h
split up work.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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Moves the Mellanox driver into drivers/net/ethernet/mellanox/ and
make the necessary Kconfig and Makefile changes.
CC: Roland Dreier <roland@kernel.org>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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