linux-kernel - Re: IO errors after "block: remove bio_get_nr

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Message-ID: <3c353dc4883c60ee99caa4555c81b6a1@lycos.com>
Date:	Mon, 21 Dec 2015 09:43:22 +0500
From:	"Artem S. Tashkinov" <t.artem@...os.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ming Lei <tom.leiming@...il.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Christoph Hellwig <hch@....de>,
	Ming Lin <ming.l@....samsung.com>, Jens Axboe <axboe@...com>,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Tejun Heo <tj@...nel.org>, IDE-ML <linux-ide@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linus971@...il.com
Subject: Re: IO errors after "block: remove bio_get_nr_vecs()"

On 2015-12-21 09:32, Linus Torvalds wrote:
> On Sun, Dec 20, 2015 at 5:50 PM, Artem S. Tashkinov wrote:
>> 
>> P.S. I know Linus doesn't condone PAE but I still find it more 
>> preferrable
>> than running a mixed environment with almost zero benefit in regard to
>> performance and quite obvious performance regressions related to an
>> increased number of libraries being loaded (i686 + x86_64) and 
>> slightly
>> bloated code which sometimes cannot fit in the CPU cache. Call me old
>> fashioned but I won't upgrade to x86_64 until most of the things that 
>> I run
>> locally are available for x86_64 and that won't happen any time soon.
> 
> Don't upgrade *user* land. User land doesn't use the braindamage that 
> is PAE.
> 
> Just run a 64-bit kernel. Keep all your 32-bit userland apps and 
> libraries.
> 
> Trust me, that *will* be faster. PAE works really horribly badly,
> because all your really important data structures like your inodes and
> directory cache will all be in the low 1GB even if you have 16BG of
> RAM.
> 
> Of course, I'd also like more people to run things that way just to
> get more coverage of the whole "yes, we do all the compat stuff
> correctly". So I have some other reasons to prefer people running
> 64-bit kernels with 32-bit user land. But PAE really is a disaster.
> 

In the past I happily ran an x86_64 bit kernel together with 32bit 
userland for quite some time but then I hit a wall: VirtualBox expects 
its kernel modules to have the same bitness as the application itself so 
I had to revert back to an i686 PAE setup. It's probably high time to 
try qemu however last time I looked at it a few years ago it lacked 
several crucial features I need from a VM.
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