lkml.org 
[lkml]   [2020]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 02/19] mm: memcg: prepare for byte-sized vmstat items
On Wed, Apr 22, 2020 at 01:46:51PM -0700, Roman Gushchin wrote:
> To implement per-object slab memory accounting, we need to
> convert slab vmstat counters to bytes. Actually, out of
> 4 levels of counters: global, per-node, per-memcg and per-lruvec
> only two last levels will require byte-sized counters.
> It's because global and per-node counters will be counting the
> number of slab pages, and per-memcg and per-lruvec will be
> counting the amount of memory taken by charged slab objects.
>
> Converting all vmstat counters to bytes or even all slab
> counters to bytes would introduce an additional overhead.
> So instead let's store global and per-node counters
> in pages, and memcg and lruvec counters in bytes.
>
> To make the API clean all access helpers (both on the read
> and write sides) are dealing with bytes.
>
> To avoid back-and-forth conversions a new flavor of helpers
> is introduced, which always returns values in pages:
> node_page_state_pages() and global_node_page_state_pages().
>
> Actually new helpers are just reading raw values. Old helpers are
> simple wrappers, which perform a conversion if the vmstat items are
> in bytes. Because at the moment no one actually need bytes,
> there are WARN_ON_ONCE() macroses inside to warn about inappropriate
> use cases.
>
> Thanks to Johannes Weiner for the idea of having the byte-sized API
> on top of the page-sized internal storage.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

\
 
 \ /
  Last update: 2020-05-07 22:36    [W:0.201 / U:2.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site