From: Josef Bacik <josef@toxicpanda.com>
To: Dennis Zhou <dennisz@fb.com>
Cc: Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
Josef Bacik <josef@toxicpanda.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-team@fb.com, Dennis Zhou <dennisszhou@gmail.com>
Subject: Re: [PATCH v2 20/23] percpu: update free path to take advantage of contig hints
Date: Tue, 25 Jul 2017 15:38:33 -0400 [thread overview]
Message-ID: <20170725193832.GT18880@destiny> (raw)
In-Reply-To: <20170724230220.21774-21-dennisz@fb.com>
On Mon, Jul 24, 2017 at 07:02:17PM -0400, Dennis Zhou wrote:
> From: "Dennis Zhou (Facebook)" <dennisszhou@gmail.com>
>
> The bitmap allocator must keep metadata consistent. The easiest way is
> to scan after every allocation for each affected block and the entire
> chunk. This is rather expensive.
>
> The free path can take advantage of current contig hints to prevent
> scanning within the start and end block. If a scan is needed, it can
> be done by scanning backwards from the start and forwards from the end
> to identify the entire free area this can be combined with. The blocks
> can then be updated by some basic checks rather than complete block
> scans.
>
> A chunk scan happens when the freed area makes a page free, a block
> free, or spans across blocks. This is necessary as the contig hint at
> this point could span across blocks. The check uses the minimum of page
> size and the block size to allow for variable sized blocks. There is a
> tradeoff here with not updating after every free. It is possible a
> contig hint in one block can be merged with the contig hint in the next
> block. This means the contig hint can be off by up to a page. However,
> if the chunk's contig hint is contained in one block, the contig hint
> will be accurate.
>
> Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Thanks,
Josef
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next prev parent reply other threads:[~2017-07-25 19:38 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-24 23:01 [PATCH v2 00/23] percpu: replace percpu area map allocator with bitmap allocator Dennis Zhou
2017-07-24 23:01 ` [PATCH v2 01/23] percpu: setup_first_chunk enforce dynamic region must exist Dennis Zhou
2017-07-25 18:03 ` Josef Bacik
2017-07-24 23:01 ` [PATCH v2 02/23] percpu: introduce start_offset to pcpu_chunk Dennis Zhou
2017-07-25 18:04 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 03/23] percpu: remove has_reserved from pcpu_chunk Dennis Zhou
2017-07-25 18:05 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 04/23] percpu: setup_first_chunk remove dyn_size and consolidate logic Dennis Zhou
2017-07-25 18:07 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 05/23] percpu: unify allocation of schunk and dchunk Dennis Zhou
2017-07-25 18:10 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 06/23] percpu: end chunk area maps page aligned for the populated bitmap Dennis Zhou
2017-07-25 18:14 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 07/23] percpu: setup_first_chunk rename schunk/dchunk to chunk Dennis Zhou
2017-07-25 18:15 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 08/23] percpu: modify base_addr to be region specific Dennis Zhou
2017-07-25 18:24 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 09/23] percpu: combine percpu address checks Dennis Zhou
2017-07-25 18:25 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 10/23] percpu: change the number of pages marked in the first_chunk pop bitmap Dennis Zhou
2017-07-25 18:27 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 11/23] percpu: introduce nr_empty_pop_pages to help empty page accounting Dennis Zhou
2017-07-25 18:29 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 12/23] percpu: increase minimum percpu allocation size and align first regions Dennis Zhou
2017-07-25 18:33 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 13/23] percpu: generalize bitmap (un)populated iterators Dennis Zhou
2017-07-25 18:35 ` Josef Bacik
2017-07-26 14:08 ` Tejun Heo
2017-07-24 23:02 ` [PATCH v2 14/23] percpu: replace area map allocator with bitmap allocator Dennis Zhou
2017-07-25 17:36 ` [percpu] ec1f2e572e: WARNING:at_lib/list_debug.c:#__list_add_valid kernel test robot
2017-07-25 19:15 ` [PATCH v2 14/23] percpu: replace area map allocator with bitmap allocator Josef Bacik
2017-07-25 20:24 ` [PATCH updated 14/23] percpu: replace area map allocator with bitmap Dennis Zhou
2017-07-24 23:02 ` [PATCH v2 15/23] percpu: introduce bitmap metadata blocks Dennis Zhou
2017-07-25 19:20 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 16/23] percpu: add first_bit to keep track of the first free in the bitmap Dennis Zhou
2017-07-25 19:21 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 17/23] percpu: skip chunks if the alloc does not fit in the contig hint Dennis Zhou
2017-07-25 19:25 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 18/23] percpu: keep track of the best offset for contig hints Dennis Zhou
2017-07-25 19:29 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 19/23] percpu: update alloc path to only scan if contig hints are broken Dennis Zhou
2017-07-25 19:32 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 20/23] percpu: update free path to take advantage of contig hints Dennis Zhou
2017-07-25 19:38 ` Josef Bacik [this message]
2017-07-24 23:02 ` [PATCH v2 21/23] percpu: use metadata blocks to update the chunk contig hint Dennis Zhou
2017-07-25 19:40 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 22/23] percpu: update pcpu_find_block_fit to use an iterator Dennis Zhou
2017-07-25 19:47 ` Josef Bacik
2017-07-24 23:02 ` [PATCH v2 23/23] percpu: update header to contain bitmap allocator explanation Dennis Zhou
2017-07-25 19:49 ` Josef Bacik
2017-07-26 21:42 ` Tejun Heo
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