Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1689387

Re: [PATCH 08/10] percpu: change the number of pages marked in the first_chunk bitmaps

Show all headers | View raw

Hello,

On Sat, Jul 15, 2017 at 10:23:13PM -0400, Dennis Zhou wrote:
> From: "Dennis Zhou (Facebook)" <dennisszhou@gmail.com>
> 
> This patch changes the allocator to only mark allocated pages for the
> region the population bitmap is used for. Prior, the bitmap was marked
> completely used as the first chunk was allocated and immutable. This is
> misleading because the first chunk may not be completely filled.
> Additionally, with moving the base_addr up in the previous patch, the
> population map no longer corresponds to what is being checked.

This in isolation makes sense although the rationale isn't clear from
the description.  Is it a mere cleanup or is this needed to enable
further changes?

> pcpu_nr_empty_pop_pages is used to ensure there are a handful of free
> pages around to serve atomic allocations. A new field, nr_empty_pop_pages,
> is added to the pcpu_chunk struct to keep track of the number of empty
> pages. This field is needed as the number of empty populated pages is
> globally kept track of and deltas are used to update it. This new field
> is exposed in percpu_stats.

But I can't see why this is being added or why this is in the same
patch with the previous change.

> Now that chunk->nr_pages is the number of pages the chunk is serving, it
> is nice to use this in the work function for population and freeing of
> chunks rather than use the global variable pcpu_unit_pages.

The same goes for the above part.  It's fine to collect misc changes
into a patch when they're trivial and related in some ways but the
content of this patch seems a bit random.

Thanks.

-- 
tejun

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH 08/10] percpu: change the number of pages marked in the first_chunk bitmaps Dennis Zhou <dennisz@fb.com> - 2017-07-16 04:30 +0200
  Re: [PATCH 08/10] percpu: change the number of pages marked in the  first_chunk bitmaps Tejun Heo <tj@kernel.org> - 2017-07-17 21:30 +0200

csiph-web