From: Jens Axboe <axboe@kernel.dk>
To: Coly Li <colyli@fnnas.com>, Stephen Zhang <starzhangzsd@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>,
Sasha Levin <sashal@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
linux-bcache@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
zhangshida <zhangshida@kylinos.cn>
Subject: Re: Fwd: [PATCH v2] bcache: use bio cloning for detached device requests
Date: Tue, 20 Jan 2026 08:01:52 -0700 [thread overview]
Message-ID: <322136ff-95f6-49f6-9126-05845f25b4e8@kernel.dk> (raw)
In-Reply-To: <aW-DHlpo4dzKRB8K@studio.local>
On 1/20/26 7:46 AM, Coly Li wrote:
>> @@ -949,6 +950,11 @@ static int bcache_device_init(struct
>> bcache_device *d, unsigned int block_size,
>> BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER))
>> goto out_ida_remove;
>>
>> + if (bioset_init(&d->bio_detach, 4,
> ^^^^^-> I feel 4 might be a bit small
> here. bio_detached set is for normal IO when backing device is not
> attached to a cache device. I would suggest to set the pool size to
> 128 or 256.
Absolutely not, 4 is more than plenty. The pool elements are only ever
used if allocations fail, to guarantee forward progress. Setting aside
128 or 256 for that case is utterly wasteful, you only need a couple. 4
is a good number, if anything it should be smaller (2).
--
Jens Axboe
next prev parent reply other threads:[~2026-01-20 15:01 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260120023535.9109-1-zhangshida@kylinos.cn>
2026-01-20 2:39 ` Fwd: [PATCH v2] bcache: use bio cloning for detached device requests Stephen Zhang
2026-01-20 2:48 ` Stephen Zhang
2026-01-20 6:53 ` Fwd: " Christoph Hellwig
2026-01-20 14:46 ` Coly Li
2026-01-20 15:01 ` Jens Axboe [this message]
2026-01-21 1:34 ` Coly Li
2026-01-21 11:55 ` Stephen Zhang
2026-01-21 14:50 ` Jens Axboe
2026-01-22 3:39 ` Coly Li
2026-01-21 22:48 ` Fwd: " Kent Overstreet
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