From: Vlastimil Babka <vbabka@suse.cz>
To: David Hildenbrand <david@redhat.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Oscar Salvador <osalvador@suse.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 9/9] mm, page_alloc: optionally disable pcplists during page isolation
Date: Fri, 25 Sep 2020 13:10:05 +0200 [thread overview]
Message-ID: <2ce92f9a-eaa2-45b2-207c-46a79d6a2bde@suse.cz> (raw)
In-Reply-To: <e0ab17e9-6c05-cf32-9e2d-efbf011860a2@redhat.com>
On 9/25/20 12:54 PM, David Hildenbrand wrote:
>>> --- a/mm/page_isolation.c
>>> +++ b/mm/page_isolation.c
>>> @@ -15,6 +15,22 @@
>>> #define CREATE_TRACE_POINTS
>>> #include <trace/events/page_isolation.h>
>>>
>>> +void zone_pcplist_disable(struct zone *zone)
>>> +{
>>> + down_read(&pcp_batch_high_lock);
>>> + if (atomic_inc_return(&zone->pcplist_disabled) == 1) {
>>> + zone_update_pageset_high_and_batch(zone, 0, 1);
>>> + __drain_all_pages(zone, true);
>>> + }
>> Hm, if one CPU is still inside the if-clause, the other one would
>> continue, however pcp wpould not be disabled and zones not drained when
>> returning.
Ah, well spotted, thanks!
>> (while we only allow a single Offline_pages() call, it will be different
>> when we use the function in other context - especially,
>> alloc_contig_range() for some users)
>>
>> Can't we use down_write() here? So it's serialized and everybody has to
>> properly wait. (and we would not have to rely on an atomic_t)
> Sorry, I meant down_write only temporarily in this code path. Not
> keeping it locked in write when returning (I remember there is a way to
> downgrade).
Hmm that temporary write lock would still block new callers until previous
finish with the downgraded-to-read lock.
But I guess something like this would work:
retry:
if (atomic_read(...) == 0) {
// zone_update... + drain
atomic_inc(...);
else if (atomic_inc_return == 1)
// atomic_cmpxchg from 0 to 1; if that fails, goto retry
Tricky, but races could only read to unnecessary duplicated updates + flushing
but nothing worse?
Or add another spinlock to cover this part instead of the temp write lock...
next prev parent reply other threads:[~2020-09-25 11:23 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 14:37 [PATCH 0/9] disable pcplists during memory offline Vlastimil Babka
2020-09-22 14:37 ` [PATCH 1/9] mm, page_alloc: clean up pageset high and batch update Vlastimil Babka
2020-09-25 10:18 ` David Hildenbrand
2020-10-05 12:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 2/9] mm, page_alloc: calculate pageset high and batch once per zone Vlastimil Babka
2020-10-05 12:52 ` Michal Hocko
2020-10-06 22:04 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 3/9] mm, page_alloc: remove setup_pageset() Vlastimil Babka
2020-09-25 10:19 ` David Hildenbrand
2020-10-05 12:59 ` Michal Hocko
2020-10-06 22:11 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 4/9] mm, page_alloc: simplify pageset_update() Vlastimil Babka
2020-09-25 10:23 ` David Hildenbrand
2020-10-05 13:20 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 5/9] mm, page_alloc: make per_cpu_pageset accessible only after init Vlastimil Babka
2020-09-25 10:25 ` David Hildenbrand
2020-10-05 13:24 ` Michal Hocko
2020-10-06 22:28 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 6/9] mm, page_alloc: cache pageset high and batch in struct zone Vlastimil Babka
2020-09-25 10:34 ` David Hildenbrand
2020-10-06 22:31 ` Vlastimil Babka
2020-10-05 13:28 ` Michal Hocko
2020-10-06 22:34 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 7/9] mm, page_alloc: move draining pcplists to page isolation users Vlastimil Babka
2020-09-25 10:39 ` David Hildenbrand
2020-10-05 13:57 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 8/9] mm, page_alloc: drain all pcplists during memory offline Vlastimil Babka
2020-09-25 10:46 ` David Hildenbrand
2020-10-05 14:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 9/9] mm, page_alloc: optionally disable pcplists during page isolation Vlastimil Babka
2020-09-25 10:53 ` David Hildenbrand
2020-09-25 10:54 ` David Hildenbrand
2020-09-25 11:10 ` Vlastimil Babka [this message]
2020-10-01 8:47 ` David Hildenbrand
2020-10-05 14:05 ` Michal Hocko
2020-10-05 14:22 ` Vlastimil Babka
2020-10-05 16:56 ` Michal Hocko
2020-10-06 8:34 ` Michal Hocko
2020-10-06 8:40 ` David Hildenbrand
2020-10-06 10:05 ` Michal Hocko
2020-09-22 17:15 ` [PATCH 0/9] disable pcplists during memory offline David Hildenbrand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2ce92f9a-eaa2-45b2-207c-46a79d6a2bde@suse.cz \
--to=vbabka@suse.cz \
--cc=david@redhat.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mhocko@suse.com \
--cc=osalvador@suse.de \
--cc=pasha.tatashin@soleen.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).