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Date: Sat, 13 Apr 2013 01:35:08 +0200
From: Adam Nowacki <nowakpl@platinum.linux.pl>
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To: Andriy Gapon <avg@FreeBSD.org>
Subject: Re: ZFS slow reads for unallocated blocks
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http://tepeserwery.pl/nowak/freebsd/zfs_sparse_optimization.patch.txt

Does it look sane?

On 2013-04-12 09:03, Andriy Gapon wrote:
>
> ENOTIME to really investigate, but here is a basic profile result for those
> interested:
>                kernel`bzero+0xa
>                kernel`dmu_buf_hold_array_by_dnode+0x1cf
>                kernel`dmu_read_uio+0x66
>                kernel`zfs_freebsd_read+0x3c0
>                kernel`VOP_READ_APV+0x92
>                kernel`vn_read+0x1a3
>                kernel`vn_io_fault+0x23a
>                kernel`dofileread+0x7b
>                kernel`sys_read+0x9e
>                kernel`amd64_syscall+0x238
>                kernel`0xffffffff80747e4b
>
> That's where > 99% of time is spent.
>