From: Christoph Hellwig <hch@infradead.org>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Christoph Hellwig <hch@infradead.org>, Qu Wenruo <wqu@suse.com>,
linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 0/2] btrfs: reduce div64 calls for __btrfs_map_block() and its variants
Date: Sun, 5 Feb 2023 23:02:26 -0800 [thread overview]
Message-ID: <Y+CmAqw7JTYwvbTR@infradead.org> (raw)
In-Reply-To: <46998577-18fd-1854-8509-b1a4e330995b@gmx.com>
On Mon, Feb 06, 2023 at 02:58:55PM +0800, Qu Wenruo wrote:
> Right, I focused too much on the perf part, but sometimes the perf part may
> sound more scary:
>
> For example, DIVQ on Skylake has latency of 42-95 cycles [1] (and
> reciprocal throughput of 24-90), for 64-bits inputs.
>
> I'm not sure what's the best way to benchmark such thing.
> Maybe just do such division with random numbers and run it at module load
> time to verify the perf?
Honestly, getting rid of the ugly divisions calls is probably
reason enough as the series looks like a nice cleanup. I just had
to nipick on the sentence.
prev parent reply other threads:[~2023-02-06 7:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-05 8:53 [PATCH 0/2] btrfs: reduce div64 calls for __btrfs_map_block() and its variants Qu Wenruo
2023-02-05 8:53 ` [PATCH 1/2] btrfs: remove map_lookup->stripe_len Qu Wenruo
2023-02-06 6:39 ` Christoph Hellwig
2023-02-06 8:28 ` Johannes Thumshirn
2023-02-06 8:50 ` Qu Wenruo
2023-02-06 8:56 ` Johannes Thumshirn
2023-02-05 8:53 ` [PATCH 2/2] btrfs: reduce div64 calls by limiting the number of stripes of a chunk to u32 Qu Wenruo
2023-02-05 12:09 ` kernel test robot
2023-02-05 12:20 ` kernel test robot
2023-02-06 6:44 ` Christoph Hellwig
2023-02-06 10:16 ` Qu Wenruo
2023-02-06 6:38 ` [PATCH 0/2] btrfs: reduce div64 calls for __btrfs_map_block() and its variants Christoph Hellwig
2023-02-06 6:58 ` Qu Wenruo
2023-02-06 7:02 ` Christoph Hellwig [this message]
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