linux-kernel - Re: [PATCH v2] aio: convert active

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Message-ID: <20210919145645.GE16005@kvack.org>
Date:   Sun, 19 Sep 2021 10:56:45 -0400
From:   Benjamin LaHaise <bcrl@...ck.org>
To:     Hamza Mahfooz <someguy@...ective-light.com>
Cc:     linux-kernel@...r.kernel.org,
        kernel test robot <yujie.liu@...el.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-aio@...ck.org
Subject: Re: [PATCH v2] aio: convert active_reqs into a hashtable

On Sun, Sep 19, 2021 at 10:41:46AM -0400, Hamza Mahfooz wrote:
> Commit 833f4154ed56 ("aio: fold lookup_kiocb() into its sole caller")
> suggests that, the fact that active_reqs is a linked-list means aio_kiocb
> lookups in io_cancel() are inefficient. So, to get faster lookups (on
> average) while maintaining similar insertion and deletion characteristics,
> turn active_reqs into a hashtable.

You're doing this wrong.  If you want faster cancellations, stash an index
into iocb->aio_key to index into an array with all requests rather than
using a hash table.

		-ben
-- 
"Thought is the essence of where you are now."