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Re: Failing XFS memory allocation

To: Nikolay Borisov <kernel@xxxxxxxx>
Subject: Re: Failing XFS memory allocation
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 25 Mar 2016 08:58:58 +1100
Cc: Brian Foster <bfoster@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <56F3B157.2060505@xxxxxxxx>
References: <56F26CCE.6010502@xxxxxxxx> <20160323124312.GB43073@xxxxxxxxxxxxxxx> <56F29279.70600@xxxxxxxx> <20160323131059.GC43073@xxxxxxxxxxxxxxx> <20160323230002.GY30721@dastard> <56F3B157.2060505@xxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Mar 24, 2016 at 11:20:23AM +0200, Nikolay Borisov wrote:
> On 03/24/2016 01:00 AM, Dave Chinner wrote:
> > As it is, yes, the memory allocation problem is with the in-core
> > extent tree, and we've known about it for some time. The issue is
> > that as memory gets fragmented, the top level indirection array
> > grows too large to be allocated as a contiguous chunk. When this
> > happens really depends on memory load, uptime and the way the extent
> > tree is being modified.
> 
> And what about the following completely crazy idea of switching order >
> 3 allocations to using vmalloc? I know this would incur heavy
> performance hit, but other than that would it cause correctness issues?
> Of course I'm not saying this should be implemented in upstream rather
> whether it's worth it having a go for experimenting with this idea.

It's not an option as many supported platforms which have extremely
limited vmalloc space.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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