linux-kernel - Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

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Date:	Thu, 11 Aug 2016 19:32:55 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	Christoph Hellwig <hch@....de>,
	"Huang, Ying" <ying.huang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Bob Peterson <rpeterso@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, LKP <lkp@...org>
Subject: Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

On Thu, Aug 11, 2016 at 7:23 PM, Dave Chinner <david@...morbit.com> wrote:
>
> And, as usual, that's the answer. Here's the reproducer:
>
> # sudo mkfs.xfs -f -m crc=0 /dev/pmem1
> # sudo mount -o noatime /dev/pmem1 /mnt/scratch
> # sudo xfs_io -f -c "pwrite 0 512m -b 1" /mnt/scratch/fooey

Heh. Ok, so 1 byte or 1kB at a time is pretty much the same thing, yeah.

And I guess that also explains why the system call entry showed up so
high in the profiles.

I'l take another look at tree_lock tomorrow, but it sounds like this
particular AIM regression is now effectively a solved (or at least
known) issue. Thanks,

              Linus