From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Martin Wilck <martin.wilck@suse.com>
Subject: Re: [PATCH] lib/sbitmap: kill 'depth' from sbitmap_word
Date: Mon, 10 Jan 2022 10:38:41 +0800 [thread overview]
Message-ID: <YducMfW4vhk15CMq@T590> (raw)
In-Reply-To: <020ba538-bb41-c827-1290-c2939bf8940c@kernel.dk>
On Sun, Jan 09, 2022 at 06:54:21PM -0700, Jens Axboe wrote:
> On 1/9/22 6:50 PM, Ming Lei wrote:
> > Only the last sbitmap_word can have different depth, and all the others
> > must have same depth of 1U << sb->shift, so not necessary to store it in
> > sbitmap_word, and it can be retrieved easily and efficiently by adding
> > one internal helper of __map_depth(sb, index).
> >
> > Not see performance effect when running iops test on null_blk.
> >
> > This way saves us one cacheline(usually 64 words) per each sbitmap_word.
>
> We probably want to kill the ____cacheline_aligned_in_smp from 'word' as
> well.
But sbitmap_deferred_clear_bit() is called in put fast path, then the
cacheline becomes shared with get path, and I guess this way isn't
expected.
Thanks,
Ming
next prev parent reply other threads:[~2022-01-10 2:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-10 1:50 [PATCH] lib/sbitmap: kill 'depth' from sbitmap_word Ming Lei
2022-01-10 1:54 ` Jens Axboe
2022-01-10 2:38 ` Ming Lei [this message]
2022-01-10 2:43 ` Jens Axboe
2022-01-10 2:47 ` Ming Lei
2022-01-10 2:49 ` Jens Axboe
2022-01-10 16:22 ` Martin Wilck
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