linux-kernel - Re: [Pcihpd-discuss] [PATCH 2/5] Construct one fakephp slot per pci slot

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Message-ID: <20071114150112.GD7523@ldl.fc.hp.com>
Date:	Wed, 14 Nov 2007 08:01:12 -0700
From:	Alex Chiang <achiang@...com>
To:	Rolf Eike Beer <eike-hotplug@...tec.de>
Cc:	pcihpd-discuss@...ts.sourceforge.net, gregkh@...e.de,
	kristen.c.accardi@...el.com, lenb@...nel.org, matthew@....cx,
	rick.jones2@...com, linux-kernel@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, linux-acpi@...r.kernel.org
Subject: Re: [Pcihpd-discuss] [PATCH 2/5] Construct one fakephp slot per
	pci slot

Hi Eike,

* Rolf Eike Beer <eike-hotplug@...tec.de>:
> Am Mittwoch, 14. November 2007 schrieb Alex Chiang:
> > * Rolf Eike Beer <eike-hotplug@...tec.de>:
> > >
> > > This is ugly. Please do it the way we already do e.g. for
> > > acpiphp: add a char[8] to "struct dummy_slot" and just
> > > reference that here.
> >
> > I took at look at the code in acpiphp you're talking about,
> > and I'm not sure why you think the above is "ugly". We're
> > talking about a runtime vs compile time storage for the name,
> > and doing a kmalloc/sprintf is a pretty standard idiom.
> >
> > BTW, I did incorporate both Linas' and Willy's comments, by
> > changing the kmalloc size to an explicit 32, and using
> > snprintf instead.
> >
> > In any case, for your particular comment, I think I'm going
> > to leave it alone for now, and let Greg weigh in with the
> > final recommendation.
> 
> Because we have another allocation of very small size for every
> slot here.
> 
> struct dummy_slot has a size of 4 pointers, that's 16 byte for
> 32 bit architectures. Putting 8 byte of additional storage here
> would save a complete allocation on 32 bit platforms. For 64
> bit platforms the memory usage is the same but we do less
> allocations (i.e. less points to fail) and less memory
> fragmentation.
> 
> Btw: your code lacks a check if kmalloc() returns NULL.

Good points. I'll make your suggested change for v2.

Thanks.

/ac

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