From: Greg Thelen <gthelen@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>, Shaohua Li <shli@fb.com>,
linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH] memcg: convert threshold to bytes
Date: Wed, 07 Oct 2015 08:56:34 -0700 [thread overview]
Message-ID: <xr93bnca1xl9.fsf@gthelen.mtv.corp.google.com> (raw)
In-Reply-To: <20151007005820.54a0b2da.akpm@linux-foundation.org>
Andrew Morton wrote:
> On Wed, 7 Oct 2015 09:30:02 +0200 Michal Hocko <mhocko@kernel.org> wrote:
>
>> On Tue 06-10-15 12:22:25, Andrew Morton wrote:
>> > On Tue, 6 Oct 2015 19:01:23 +0200 Michal Hocko <mhocko@kernel.org> wrote:
>> >
>> > > On Mon 05-10-15 14:44:22, Shaohua Li wrote:
>> > > > The page_counter_memparse() returns pages for the threshold, while
>> > > > mem_cgroup_usage() returns bytes for memory usage. Convert the threshold
>> > > > to bytes.
>> > > >
>> > > > Looks a regression introduced by 3e32cb2e0a12b69150
>> > >
>> > > Yes. This suggests
>> > > Cc: stable # 3.19+
>> >
>> > But it's been this way for 2 years and nobody noticed it. How come?
>>
>> Maybe we do not have that many users of this API with newer kernels.
>
> Either it's zero or all the users have worked around this bug.
>
>> > Or at least, nobody reported it. Maybe people *have* noticed it, and
>> > adjusted their userspace appropriately. In which case this patch will
>> > cause breakage.
>>
>> I dunno, I would rather have it fixed than keep bug to bug compatibility
>> because they would eventually move to a newer kernel one day when they
>> see the "breakage" anyway.
>
> They'd only see breakage if we fixed this in the newer kernel.
>
> We could just change the docs and leave it as-is. That it is called
> "usage_in_bytes" makes that a bit awkward.
>
> A bit of googling indicates that people are using usage_in_bytes. A
> few. All the discussions I found clearly predate this bug.
>
> So did people just stop using this? Is there some alternative way of
> getting the same info?
We (Google) are using byte based notifications on memory.limit_in_bytes
on a pre 3e32cb2e0a12b69150 kernel. So we'd notice the regression when
running newer kernels.
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prev parent reply other threads:[~2015-10-07 15:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-05 21:44 Shaohua Li
2015-10-05 22:03 ` Andrew Morton
2015-10-06 17:01 ` Michal Hocko
2015-10-06 19:22 ` Andrew Morton
2015-10-07 7:30 ` Michal Hocko
2015-10-07 7:58 ` Andrew Morton
2015-10-07 8:30 ` Michal Hocko
2015-10-07 15:25 ` Shaohua Li
2015-10-07 15:56 ` Greg Thelen [this message]
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