Messages in this thread | | | Date | Wed, 6 Nov 2013 03:42:20 -0500 (EST) | From | Jerome Marchand <> | Subject | Re: [PATCH v4 2/2] mm: allow to set overcommit ratio more precisely |
| |
----- Original Message ----- > From: "Andrew Morton" <akpm@linux-foundation.org> > To: "Jerome Marchand" <jmarchan@redhat.com> > Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "dave hansen" <dave.hansen@intel.com> > Sent: Wednesday, November 6, 2013 12:53:19 AM > Subject: Re: [PATCH v4 2/2] mm: allow to set overcommit ratio more precisely > > On Fri, 18 Oct 2013 14:56:59 +0200 Jerome Marchand <jmarchan@redhat.com> > wrote: > > > Some applications that run on HPC clusters are designed around the > > availability of RAM and the overcommit ratio is fine tuned to get the > > maximum usage of memory without swapping. With growing memory, the 1% > > of all RAM grain provided by overcommit_ratio has become too coarse > > for these workload (on a 2TB machine it represents no less than > > 20GB). > > > > This patch adds the new overcommit_ratio_ppm sysctl variable that > > allow to set overcommit ratio with a part per million precision. > > The old overcommit_ratio variable can still be used to set and read > > the ratio with a 1% precision. That way, overcommit_ratio interface > > isn't broken in any way that I can imagine. > > The way we've permanently squished this mistake in the past is to > switch to "bytes". See /proc/sys/vm/*bytes. > > Would that approach work in this case? >
That was my first version of this patch (actually "kbytes" to avoid overflow). Dave raised the issue that it silently breaks the user interface: overcommit_ratio is zero while the system behaves differently.
Jerome
| |