linux-kernel - Re: [RFC PATCH v2 0/2] introduce io_uring_cmd_import_fixed

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Message-ID: <Z9Lj8s-pTTEJhMOn@sidongui-MacBookPro.local>
Date: Thu, 13 Mar 2025 22:56:02 +0900
From: Sidong Yang <sidong.yang@...iosa.ai>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
	Jens Axboe <axboe@...nel.dk>, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, io-uring@...r.kernel.org
Subject: Re: [RFC PATCH v2 0/2] introduce io_uring_cmd_import_fixed_vec

On Thu, Mar 13, 2025 at 01:17:44PM +0000, Pavel Begunkov wrote:
> On 3/13/25 13:15, Pavel Begunkov wrote:
> > On 3/13/25 10:44, Sidong Yang wrote:
> > > On Thu, Mar 13, 2025 at 08:57:45AM +0000, Pavel Begunkov wrote:
> > > > On 3/12/25 14:23, Sidong Yang wrote:
> > > > > This patche series introduce io_uring_cmd_import_vec. With this function,
> > > > > Multiple fixed buffer could be used in uring cmd. It's vectored version
> > > > > for io_uring_cmd_import_fixed(). Also this patch series includes a usage
> > > > > for new api for encoded read in btrfs by using uring cmd.
> > > > 
> > > > Pretty much same thing, we're still left with 2 allocations in the
> > > > hot path. What I think we can do here is to add caching on the
> > > > io_uring side as we do with rw / net, but that would be invisible
> > > > for cmd drivers. And that cache can be reused for normal iovec imports.
> > > > 
> > > > https://github.com/isilence/linux.git regvec-import-cmd
> > > > (link for convenience)
> > > > https://github.com/isilence/linux/tree/regvec-import-cmd
> > > > 
> > > > Not really target tested, no btrfs, not any other user, just an idea.
> > > > There are 4 patches, but the top 3 are of interest.
> > > 
> > > Thanks, I justed checked the commits now. I think cache is good to resolve
> > > this without allocation if cache hit. Let me reimpl this idea and test it
> > > for btrfs.
> > 
> > Sure, you can just base on top of that branch, hashes might be
> > different but it's identical to the base it should be on. Your
> > v2 didn't have some more recent merged patches.
> 
> Jens' for-6.15/io_uring-reg-vec specifically, but for-next likely
> has it merged.

Yes, there is commits about io_uring-reg-vec in Jens' for-next. I'll make v3 based
on the branch.

> 
> -- 
> Pavel Begunkov
>