From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: brookxu <brookxu.cn@gmail.com>
Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org
Subject: Re: [PATCH RESEND 4/8] ext4: add the gdt block of meta_bg to system_zone
Date: Tue, 8 Dec 2020 23:34:15 -0500 [thread overview]
Message-ID: <20201209043415.GG52960@mit.edu> (raw)
In-Reply-To: <4770d6b2-bb9f-7bc5-4fbd-2104bfeba7c2@gmail.com>
On Fri, Dec 04, 2020 at 09:26:49AM +0800, brookxu wrote:
>
> Theodore Y. Ts'o wrote on 2020/12/3 23:08:
> > On Sat, Nov 07, 2020 at 11:58:14PM +0800, Chunguang Xu wrote:
> >> From: Chunguang Xu <brookxu@tencent.com>
> >>
> >> In order to avoid poor search efficiency of system_zone, the
> >> system only adds metadata of some sparse group to system_zone.
> >> In the meta_bg scenario, the non-sparse group may contain gdt
> >> blocks. Perhaps we should add these blocks to system_zone to
> >> improve fault tolerance without significantly reducing system
> >> performance.
>
> Thanks, in the large-market scenario, if we deal with all groups,
> the system_zone will be very large, which may reduce performance.
> I think the previous method is good, but it needs to be changed
> slightly, so that the fault tolerance in the meta_bg scenario
> can be improved without the risk of performance degradation.
OK, I see. But this is not actually reliable:
> >> + if ((i < 5) || ((i % flex_size) == 0)) {
This only works if the flex_size is less than or equal to 64 (assuming
a 4k blocksize). That's because on 64-bit file systems, we can fit 64
block group descripters in a 4k block group descriptor block, so
that's the size of the meta_bg. The default flex_bg size is 16, but
it's quite possible to create a file system via "mke2fs -t ext4 -G
256". In that case, the flex_size will be 256, and we would not be
including all of the meta_bg groups. So i % flex_size needs to be
replaced by "i % meta_bg_size", where meta_bg_size would be
initialized to EXT4_DESC_PER_BLOCK(sb).
Does that make sense?
- Ted
next prev parent reply other threads:[~2020-12-09 4:35 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-07 15:58 [PATCH RESEND 1/8] ext4: use ext4_assert() to replace J_ASSERT() Chunguang Xu
2020-11-07 15:58 ` [PATCH RESEND 2/8] ext4: remove redundant mb_regenerate_buddy() Chunguang Xu
2020-12-03 14:42 ` Theodore Y. Ts'o
2020-11-07 15:58 ` [PATCH RESEND 3/8] ext4: simplify the code of mb_find_order_for_block Chunguang Xu
2020-12-03 14:43 ` Theodore Y. Ts'o
2020-11-07 15:58 ` [PATCH RESEND 4/8] ext4: add the gdt block of meta_bg to system_zone Chunguang Xu
2020-12-03 15:08 ` Theodore Y. Ts'o
2020-12-04 1:26 ` brookxu
2020-12-09 4:34 ` Theodore Y. Ts'o [this message]
2020-12-09 11:48 ` brookxu
2020-12-09 19:39 ` Theodore Y. Ts'o
2020-12-10 11:00 ` brookxu
2020-12-15 1:14 ` brookxu
2020-12-15 20:13 ` Theodore Y. Ts'o
2020-12-17 16:01 ` Andreas Dilger
2020-12-04 1:29 ` brookxu
2020-11-07 15:58 ` [PATCH RESEND 5/8] ext4: update ext4_data_block_valid related comments Chunguang Xu
2020-12-09 19:11 ` Theodore Y. Ts'o
2020-11-07 15:58 ` [PATCH 6/8] ext4: add a helper function to validate metadata block Chunguang Xu
2020-12-09 4:55 ` Theodore Y. Ts'o
2020-12-09 12:12 ` brookxu
2020-11-07 15:58 ` [PATCH RESEND 7/8] ext4: delete invalid code inside ext4_xattr_block_set() Chunguang Xu
2020-12-09 19:24 ` Theodore Y. Ts'o
2020-11-07 15:58 ` [PATCH RESEND 8/8] ext4: fix a memory leak of ext4_free_data Chunguang Xu
2020-12-09 19:29 ` Theodore Y. Ts'o
2020-12-03 14:38 ` [PATCH RESEND 1/8] ext4: use ext4_assert() to replace J_ASSERT() Theodore Y. Ts'o
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