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Re: [PATCH 0/2] xfs: fix some new memory allocation failures

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 0/2] xfs: fix some new memory allocation failures
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Tue, 03 Sep 2013 17:38:17 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130903211643.GG23571@dastard>
References: <1378119180-31380-1-git-send-email-david@xxxxxxxxxxxxx> <5224C4E9.8080604@xxxxxxx> <20130902222004.GI12779@dastard> <5225DF07.4080509@xxxxxxx> <20130903200401.GF23571@dastard> <52264AA0.4010501@xxxxxxx> <20130903211643.GG23571@dastard>
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On 09/03/13 16:16, Dave Chinner wrote:
Let's just quote Linus from 2003, shall we:

http://yarchive.net/comp/linux/vmalloc.html

|>  I think it'd make more sense to only use vmalloc when it's explicitly
|>  too big for kmalloc - or simply switch on num_online_cpus>  100 or
|>  whatever a sensible cutoff is (ie nobody but you would ever see this ;-))
|
| No, please please please don't do these things.
|
| vmalloc() is NOT SOMETHING YOU SHOULD EVER USE! It's only valid for when
| you_need_  a big array, and you don't have any choice. It's slow, and it's
| a very restricted resource: it's a global resource that is literally
| restricted to a few tens of megabytes. It should be_very_  carefully used.
|
| There are basically no valid new uses of it. There's a few valid legacy
| users (I think the file descriptor array), and there are some drivers that
| use it (which is crap, but drivers are drivers), and it's_really_  valid
| only for modules. Nothing else.
|
| Basically: if you think you need more memory than a kmalloc() can give,
| you need to re-organize your data structures. To either not need a big
| area, or to be able to allocate it in chunks.
|
|               Linus

Linus will say exactly the same thing today....

And that is very very sad that is it funny.

--Mark.

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