----- Original Message ----- > From: "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx> > To: "Jerome Marchand" <jmarchan@xxxxxxxxxx> > Cc: linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, "dave hansen" <dave.hansen@xxxxxxxxx> > 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@xxxxxxxxxx> > 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>