RE: [f2fs-dev] [PATCH 9/9] f2fs: update extent tree in batches

[Chao Yu <chao2.yu@samsung.com>]

> -----Original Message-----
> From: Chao Yu [mailto:chao2.yu@samsung.com]
> Sent: Friday, August 21, 2015 8:55 PM
> To: 'Jaegeuk Kim'
> Cc: linux-kernel@vger.kernel.org; linux-f2fs-devel@lists.sourceforge.net
> Subject: Re: [f2fs-dev] [PATCH 9/9] f2fs: update extent tree in batches
> 
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Friday, August 21, 2015 1:48 AM
> > To: Chao Yu
> > Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH 9/9] f2fs: update extent tree in batches
> >
> > Hi Chao,
> >
> > On Wed, Aug 19, 2015 at 07:21:48PM +0800, Chao Yu wrote:
> > > This patch introduce a new helper f2fs_update_extent_tree_range
> > > which can update extent nodes in extent tree in batches.
> > >
> > > Now, we use the function to invalidate blocks in batches instead of
> > > invalidating them one by one when truncating blocks.
> >
> > IMO, it's not clear the benefit of this patch in terms of performance and code
> > readability versus risky code changes.
> 
> This is only used in truncate path, IMO, in theory, we can gain benefit from
> this batch mode operation when truncating frequently.
> 
> I will test the patch for numbers.

Since in batched operation is only used in truncation path, I only stat data
in that path. And I add below function to test for stating time count.

uint64_t rdtsc(void)
{
	uint32_t lo, hi;
	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
	return (uint64_t)hi << 32 | lo;
}

My test environment is: ubuntu, intel i7-3770, 16G memory, 256g micron ssd.

a) Removing 128MB file which has one extent node mapping whole range of file:
1. dd if=/dev/zero  of=/mnt/f2fs/128M bs=1M count=128
2. sync
3. rm /mnt/f2fs/128M
											count			total
average
f2fs_update_extent_tree_range		33				3321			100.63
f2fs_update_extent_cache				32768			7651022		233.49

b) fsstress:
fsstress -d /mnt/f2fs -l 5 -n 100 -p 20
											count			total
average
f2fs_update_extent_tree_range		1868			1073762		574.82
f2fs_update_extent_cache				31518			11495827		364.74

Thanks,