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Groups > linux.kernel > #1325607
| Path | csiph.com!goblin3!goblin1!goblin.stu.neva.ru!news.mixmin.net!aioe.org!bofh.it!news.nic.it!robomod |
|---|---|
| From | Johannes Weiner <hannes@cmpxchg.org> |
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] mm: vmpressure: make vmpressure_window a tunable. |
| Date | Wed, 03 Feb 2016 17:20:03 +0100 |
| Message-ID | <qY8jV-4ft-35@gated-at.bofh.it> (permalink) |
| References | <qY3tU-19p-13@gated-at.bofh.it> |
| X-Original-To | Martijn Coenen <maco@google.com> |
| MIME-Version | 1.0 |
| Content-Type | text/plain; charset=us-ascii |
| Content-Disposition | inline |
| User-Agent | Mutt/1.5.24 (2015-08-30) |
| Sender | robomod@news.nic.it |
| List-ID | <linux-kernel.vger.kernel.org> |
| X-Mailing-List | linux-kernel@vger.kernel.org |
| Approved | robomod@news.nic.it |
| Lines | 36 |
| Organization | linux.* mail to news gateway |
| X-Original-Cc | linux-mm@kvack.org, Anton Vorontsov <anton@enomsg.org>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, Vladimir Davydov <vdavydov@virtuozzo.com>, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Jonathan Corbet <corbet@lwn.net> |
| X-Original-Date | Wed, 3 Feb 2016 11:19:10 -0500 |
| X-Original-Message-ID | <20160203161910.GA10440@cmpxchg.org> |
| X-Original-References | <001a114b360c7fdb9b052adb91d6@google.com> |
| X-Original-Sender | linux-kernel-owner@vger.kernel.org |
| Xref | csiph.com linux.kernel:1325607 |
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On Wed, Feb 03, 2016 at 11:06:20AM +0100, Martijn Coenen wrote: > The window size used for calculating vm pressure > events was previously fixed at 512 pages. The > window size has a big impact on the rate of notifications > sent off to userspace, in particular when using the > "low" level. On machines with a lot of memory, the > current value may be excessive. > > On the other hand, making the window size depend on > machine size does not allow userspace to change the > notification rate based on the current state of the > system. For example, when a lot of memory is still > available, userspace may want to increase the window > since it's not interested in receiving notifications > for every 2MB scanned. > > This patch makes vmpressure_window a sysctl tunable. If the machine is just cleaning up use-once cache, frequent events make no sense. And if the machine is struggling, the notifications better be in time. That's hardly a tunable. It's a factor that needs constant dynamic adjustment depending on VM state. The same state this mechanism is supposed to report. If we can't get this right, how will userspace? A better approach here would be to 1) find a minimum window size that makes us confident that there are no false positives - this is likely to be based on machine size, maybe the low watermark? - and 2) limit reporting of lower levels, so you're not flooded with ALLGOOD! events. VMPRESSURE_CRITICAL: report every vmpressure_win VMPRESSURE_MEDIUM: report every vmpressure_win*2 VMPRESSURE_LOW: report every vmpressure_win*4 Pick your favorite scaling factor here.
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[PATCH] mm: vmpressure: make vmpressure_window a tunable. Martijn Coenen <maco@google.com> - 2016-02-03 12:10 +0100
Re: [PATCH] mm: vmpressure: make vmpressure_window a tunable. Johannes Weiner <hannes@cmpxchg.org> - 2016-02-03 17:20 +0100
Re: [PATCH] mm: vmpressure: make vmpressure_window a tunable. Martijn Coenen <maco@google.com> - 2016-02-04 12:30 +0100
Re: [PATCH] mm: vmpressure: make vmpressure_window a tunable. Johannes Weiner <hannes@cmpxchg.org> - 2016-02-04 21:30 +0100
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