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From: antlists <antlists@youngman.org.uk>
To: Wang Shanker <shankerwangmiao@gmail.com>, linux-block@vger.kernel.org
Cc: linux-raid@vger.kernel.org
Subject: Re: [Bug Report] Discard bios cannot be correctly merged in blk-mq
Date: Sat, 5 Jun 2021 23:38:28 +0100	[thread overview]
Message-ID: <6c407281-ee90-f577-d6db-d36211b1fdc0@youngman.org.uk> (raw)
In-Reply-To: <85F98DA6-FB28-4C1F-A47D-C410A7C22A3D@gmail.com>

On 05/06/2021 21:54, Wang Shanker wrote:
> You may wonder the importance of merging discard operations. In the
> implementation of RAID456, bios are committed in 4k trunks (they call
> them as stripes in the code and the size is determined by DEFAULT_STRIPE_SIZE).
> The proper merging of the bios is of vital importance for a reasonable
> operating performance of RAID456 devices.

Note that I have seen reports (I'm not sure where or how true they are), 
that even when requests are sent as 512k or whatever, certain upper 
layers break them into 4k's, presumably expecting lower layers to merge 
them again.

You might have better luck looking for and suppressing the breaking up 
of large chunks.

Cheers,
Wol

  reply	other threads:[~2021-06-05 22:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-05 20:54 Wang Shanker
2021-06-05 22:38 ` antlists [this message]
2021-06-06  3:44   ` Wang Shanker
2021-06-07 13:07 ` Ming Lei
2021-06-08 15:49   ` Wang Shanker
2021-06-09  0:41     ` Ming Lei
2021-06-09  2:40       ` Wang Shanker
2021-06-09  8:44         ` Xiao Ni
2021-06-09  9:03           ` Wang Shanker
2021-06-18  6:28             ` Wang Shanker
2021-06-18 12:49               ` Xiao Ni
2021-06-21  7:49                 ` Wang Shanker
2021-06-22  1:48                   ` Xiao Ni

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