Messages in this thread | | | Date | Thu, 23 Mar 2006 11:37:13 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH 9 of 18] ipath - char devices for diagnostics and lightweight subnet management |
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Quoting r. Bryan O'Sullivan <bos@pathscale.com>: > > Could you please explain why is this useful? Users could not care less - > > they never have to touch an SMA. > > We have customers who use our driver who do not want a full IB stack > present, for example in embedded environments.
I understand they do, but they could just use the parts of IB stack and never notice. In my experience, embedded systems are typically diskless - why is a userspace SMA better than kernel-level one for them? The advantage would be everyone using a single kernel/user interface, common utilities for management, diagnostics ... I could go on.
So what's your point? Memory usage? Let's take a look:
ib_mad is the IB stack module that includes between other things the kernel-level SMA (BTW, if necessary, you should be able to split it out so that it is only loaded on demand):
I think IB stack is modest, as core modules go. Here's how a loaded IB stack looks like on my system:
Module Size Used by ib_mad 36260 2 ib_ipath,ib_mthca ib_core 46080 3 ib_ipath,ib_mthca,ib_mad
So there are *maximum* 82K code to save. This is a 64-bit system, I think embedded systems are usually 32 bit so there'll be just 41K.
And I don't believe you can save much since as a solution you seem to have re-implemented the full IB stack in your low level driver:
Module Size Used by ib_ipath 79256 0 ipath_core 159764 1 ib_ipath
By contrast, a low-level which doesn't reimplement IB core is just a bit above 100K.
-- Michael S. Tsirkin Staff Engineer, Mellanox Technologies - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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